introduction to genetics - xtec to genetics from proteins to mendel student worksheets unit 1 lesson...

INTRODUCTION TO GENETICS FROM PROTEINS TO MENDEL

Rosa Macaya

16/Maig/2011

INTRODUCTION TO GENETICS

From Proteins to Mendel Student worksheets Unit 1

Lesson 1.1. Should we have our four child?

Rosa Macaya IES Pobla de Segur 2

Activity 1.1.

I. Listen to the story and tick the words you hear

HAPPINESS UNHAPPINESS

TEA INFUSION BLOOD TRANSFUSION

BLOODINFUSION

BAD LUCK GOOD LUCK UNLUCKY

BLOODY BLEEDING

PARENTS GRANDPARENTS

OLDEST ELDEST

DEAD ALIVE





II. Listen to the story and take notes to draw a family tree.

Listen to the story and try to find out what the problem is.

I think that…………..

It could be…………..

Male

Female





Activity 1.2

1.2.1. Listen to the story and find out the missing words. The words

given in activity 1.1. will help you

When I was young I______ dreamt about having children. I’d never thought

that anything bad could happen to me. Even though my brother’s ____. He was

really ________. Yes, he always had bad luck… My parents suffered so much; it

was tough having to think about every little thing that Paul did. They couldn’t live

in peace all his life. Phone calls from the school saying he was ________. Mum

running to take him to hospital, _____ _________ plus all day-to-day stuff. It

was all quite normal to me. I grew up with all of this. But, even so, I did not

expect something like this to happen to me, to my children. Nobody told me that,

nobody asked when I first got pregnant. There was _________ all around, even

from my _______. They were so excited about becoming ____________; they

didn’t tell me that there was any possibility of there being any problem with my

child. But they didn’t tell me because they did not know the truth about their

own son. Poor Paul. He died years ago from AIDS, something to be ashamed of.

It wasn’t Paul’s fault. Poor Paul… all his short life affected by what he had

inherited. He didn’t choose to die; death found him… got into somebody’s _____.

Yes, somebody’s blood. How unlucky was that! Poor Paul… But nobody told me

that my own kids could have the same problem as my ______ brother, my

beloved brother. Not even the doctors told me anything. They didn’t ask me

about my family __________. (Part I (1’46’’)28 lines)

Should we have a fourth child???

Should we have a fourth child???





1.2.2 Listen to the story. Fill in the gaps and complete the family

tree you drew in activity 1.1

So I had my _____ _____. We all felt so happy. And my ______, the lovely

_____, and no problem either. But our luck seemed to run out when my

________ ___ was born. Just arrived in the world and he started to suffer. His

birth was very traumatic. I lost a lot of blood, hours and hours and my poor baby

was still bleeding. My ______ prayed. I was scared; I could not see him until

days later. My _______ could, but he didn’t tell me anything. Well, I don’t think

he knew what to say. When our son was diagnosed with “haemophilia” I didn’t

know what it meant. In hospital we were asked about our family background and

then I discovered the truth about ____. I couldn’t understand why my _______

hadn’t told me the truth about Paul’s illness, even about his death. But I don’t

think they were sure about anything. I feel sorry for them now, but then I was

very disappointed and I blamed them for my baby’s disease. If had known about

this before, then certainly I wouldn’t have had the kid. But we did not know

anything!

(Part II, (1’13’’)15 lines)

1.2.3 Listen to the story. Fill in the gaps and write two sentences

summarising the story.

It took a while for us to understand ___________. With a lot of help from all

the hospital staff we learnt to cope with it and how to bring up our

___________ child. Things have changed a lot, new products have been

discovered and I hope my youngest child’s life will be easier than his uncle’s.

Now, our Tom is already 6 years old and he seems to be controlling his

________ episodes.

I don’t know if I am a _______ or not. Neither does my husband. Though

everything points to the ____ coming from my family. I have learnt a lot about

___________. If only my parents had known more…, but I don’t think that it

was their fault. They didn’t know anything and the doctors didn’t tell them





anything; they probably thought they wouldn’t understand. It is pity to live in

such ignorance! Always believing that life is a kind of fate… But I don’t want to

live like that. I’d like to have a fourth child and I want to know what the chances

are of having a “healthy” child in spite of my ____ history. I have heard about

being able to find out, but I am not sure.

Science should be there to help to fight against our “bad” _____, shouldn’t it?

(Part III, (1’15’’) 19 lines)





SHOULD WE HAVE A FOURTH CHILD???

When I was young I always dreamt about having children. I’d never thought that

anything bad could happen to me. Even though my brother’s dead. He was really

unlucky. Yes, he always had bad luck… My parents suffered so much; it was tough

having to think about every little thing that Paul did. They couldn’t live in peace

all his life. Phone calls from the school saying he was bleeding. Mum running to

take him to hospital, blood infusions plus all day-to-day stuff. It was all quite

normal to me. I grew up with all of this. But, even so, I did not expect something

like this to happen to me, to my children. Nobody told me that, nobody asked

when I first got pregnant. There was happiness all around, even from my

parents. They were so excited about becoming grandparents; they didn’t tell me

that there was any possibility of there being any problem with my child. But they

didn’t tell me because they did not know the truth about their own son. Poor

Paul. He died years ago from AIDS, something to be ashamed of. It wasn’t Paul’s

fault. Poor Paul… all his short life affected by what he had inherited. He didn’t

choose to die; death found him… got into somebody’s blood. Yes, somebody’s

blood. How unlucky was that! Poor Paul… But nobody told me that my own kids

could have the same problem as my eldest brother, my beloved brother. Not

even the doctors told me anything. They didn’t ask me about my family

background.

So I had my first child. We all felt so happy. And my second, the lovely Helen,

and no problem either. But our luck seemed to run out when my youngest son was

born. Just arrived in the world and he started to suffer. His birth was very

traumatic. I lost a lot of blood, hours and hours and my poor baby was still

bleeding. My mother prayed. I was scared; I could not see him until days later.

My husband could, but he didn’t tell me anything. Well, I don’t think he knew

what to say. When our son was diagnosed with “haemophilia” I didn’t know what

it meant. In hospital we were asked about our family background and then I

discovered the truth about Paul. I couldn’t understand why my parents hadn’t





told me the truth about Paul’s illness, even about his death. But I don’t think

they were sure about anything. I feel sorry for them now, but then I was very

disappointed and I blamed them for my baby’s disease. If had known about this

before, then certainly I wouldn’t have had the kid. But we did not know anything!

It took a while for us to understand haemophilia. With a lot of help from all the

hospital staff we learnt to cope with it and how to bring up our haemophilic

child. Things have changed a lot, new products have been discovered and I hope

my youngest child’s life will be easier than his uncle’s.

Now, our Tom is already 6 years old and he seems to be controlling his bleeding

episodes.

I don’t know if I am a carrier or not. Neither does my husband. Though

everything points to the gene coming from my family. I have learnt a lot about

haemophilia. If only my parents had known more…, but I don’t think that it was

their fault. They didn’t know anything and the doctors didn’t tell them anything;

they probably thought they wouldn’t understand. It is pity to live in such

ignorance! Always believing that life is a kind of fate… But I don’t want to live

like that. I’d like to have a fourth child and I want to know what the chances are

of having a “healthy” child in spite of my gene history. I have heard about being

able to find out, but I am not sure.

Science should be there to help to fight against our “bad” genes, shouldn’t it?





Activity 1.2.1.

Read the following text and put the names of the family member.

Compare the information you have written on the pedigree chart in

activity 1.1.1. Paint in a different colour the members with

haemophilia.

Mrs Ann Drinkwater, born Pennymann, is a 38 years old woman with

a family history of haemophilia A. She had got a five years older

brother, Paul, who died 10 years ago after getting AIDS from a

contamined plasma infusion. She does not have further information

about other members of her family. Mrs Drinkwater’s husband,

John is 40 years old and there are not haemophilia traits in his

family. They have three children, the eldest is 12 years old called

Matthew, Helen is 10. Both of them are not haemophilic. The

youngest, Tom is 6 years old and he is haemophilic.

Ann and John Drinkwater would like to have a fourth child and they

have applied to a Genetic Cabinet to know the probability of having

another child with the disease and if there is a possibility to avoid

100% sure that the inheritance of the haemophilia using Genetic

Therapy.



Lesson 1.2. Making posters!


Activity 1.2.2. Making a poster

� Information about Haemophilia

• Causes

Haemophilia is a sex-linked disorder. Its gene is in chromosome sexual X. Since

males (XY) have only one X chromosome, so only one copy of the gene placed in

this chromosome, if the gene is they will be affected with the disease. Females

have two X chromosome (XX) only will have the disease when they have the gene

in both (rare). The probability of a woman having the disease is very low, though

possible. That would happen if both father and mother had the affected

haemophilic gene. Frequently female are only carriers because this gene is

recessive in front the normal gene. That is why the have the ability to pass the

gene on to their offspring but are not affected with the illness themselves.

• Types

There are two types of haemophilia, A and B. Haemophilia A involves a mutation

in the factor (protein) VIII blood clotting factor gene and haemophilia B

involves a mutation in the factor IX blood clotting factor gene. Both mutations

do not let the process of blood clotting happen, as it normally should.

• Symptoms

Include internal bleeding, blood in stool and urine, frequent nosebleeds, easy

bruising, and bleeding into muscles and joints that leads to chronic arthritis;

bleeding in the rain External bleeding could appears if the skins is broken by a

scrape, cut or abrasion.

• Therapy

There is not cure for haemophilia; it can be controlled with regular injections of

the deficient clotting factor, i.e., factor VIII in haemophilia A. In western

countries, common standards of care fall into two categories: prophylaxis or on-

demand. The first one involves the infusion of clotting factor in order to keep

clotting levels sufficiently high to prevent spontaneous bleeding episodes. On-

demand treatment involves treating bleeding episodes once they arise.





• Collateral problems related to haemophilia therapy

As a direct result of the contamination of the blood supply in the late 1970’s and

early 80’s with virologic agents such as HIV (Human Immunodeficiency Virus)

and Hepatitis new methods were developed in the production of clotting factor

products. The initial response was to heat treat (pasteurize) plasma-derived

concentrate, followed by the development of monoclonal factor concentrates

grown to inactivate any viral agents. More recently, recombinant factors

products (which are typically cultured in Chinese hamster ovaries and involve

little, if any contact with human plasma products) have become available and are

widely used in wealthier western countries. These products are quite safe but

also very expensive and not usually available in developing countries and

sometimes are even difficult to find in developing countries.





� Information about AIDS

• What does “AIDS” mean?

AIDS stands for Acquired Immune Deficiency Syndrome: Acquired means you can get infected with it Immune Deficiency means a weakness in the body’s system that fights

diseases. Syndrome means a group of health problems that make up a disease.

• Causes

AIDS is caused by a virus called HIV, the Human Immunodeficiency Virus. If

you get infected with HIV, your body will try to fight the infection. It will

make “antibodies,” special molecules to fight HIV. A blood test for HIV looks for these antibodies. If you have them in your

blood, it means that you have HIV infection. People who have the HIV

antibodies are called “HIV-Positive.” Fact Sheet 102 has more information

on HIV testing.

Being HIV-positive, or having HIV disease, is not the same as having AIDS.

Many people are HIV-positive but don’t get sick for many years. As HIV

disease continues, it slowly wears down the immune system. Viruses,

parasites, fungi and bacteria that usually don’t cause any problems can make

you very sick if your immune system is damaged. These are called

“opportunistic infections.” See Fact Sheet 500 for an overview of

opportunistic infections.

• How do you get AIDS?

You don’t actually “get” AIDS. You might get infected with HIV, and later

you might develop AIDS. You can get infected with HIV from anyone who’s

infected, even if they don’t look sick and even if they haven’t tested HIV-

positive yet. The blood, vaginal fluid, semen, and breast milk of people





infected with HIV has enough of the virus in it to infect other people. Most

people get the HIV virus by:

� having sex with an infected person

� sharing a needle (shooting drugs) with someone who’s infected

� being born when their mother is infected, or drinking the breast milk of

an infected womaN

� Getting an infusion of infected blood used to be a way people got AIDS,

but now the blood supply is screened very carefully and the risk is

extremely



Lesson 1.3. Making live possible...from DNA to Proteins


Review from Molecular Genetics

Activity 1.3.1

Look at the following picture…

“The Central Dogma of Molecular Biology: From DNA to RNA to Protein,,





Now…………

From the single DNA strand below, write the complementary

5’ .. t a c t a a c g t t t g t a c a a a c c g g a a a t t .. 3’

............………………………………………………………………………………………………………………….

then write the mRNA

mRNA

5’ ………………………………………………………………………………...................…………………… 3’

Look at the pictures below and write the correct name in each label





And now……….. with the help of the Genetic Code Table, translate the

RNA nucleotides’ sequence to a polypeptide sequence

You have made a protein!!!!





Activity 1.3.2 Mutations

WHAT WILL HAPPEN IF……..

…….. we change a pair nucleotides from the DNA strand….

t a c t a a c g t t t g t a c a a a c c g g a a a t g c t

.

State a hypothesis saying what could happen if you write “aa” instead

the “tt”. You can start the hypothesis…

“If I write aa, in the place of “tt” then the mRNA will be “aa” and then

………………………………………....................................................................................................

Now think of a “way” to prove your hypothesis

Write down the conclusion.

If the nucleotides’ sequence change, ......................................................................

. ...........................................................................................................................................

Now, try to do another mutation. In this case try to delete a pair

nucleotides from the DNA strand…….

Predict what will happen…. And prove it!



Lesson 1.4. Once upon a time playing with pea plants


Activity 1.3.2. SCIENTIFIC METHOD

Let’s and to relate Haemophilia (lack of an

appropriate protein) and inheritance (DNA).

Let’s work all together to write a hypothesis about this relationship and

all the steps to prove or reject our hypothesis!!

We are going to follow all the steps from the scientific method:

1. Problem – (What are you trying to figure out? Write this in the form of a

question.)

2. Hypothesis – (What do you think you are going to find out?)

3. Materials and procedure (List the materials you will use in the experiment.)

4. Results – What did you observe when you performed the experiment?

5. Conclusion – From what you observed, how would you answer your original

question?





Activity 1.4.1

a) First read your text and fill in the corresponding part of the table

below.

b) Make 3 people group (A,B&C), share the information from your text

and fill the rest of the table.

A

Date of birth

Father’s job

Grandfather’s job

Why did he have to stop studying?

Where did he continue his studies?

What did he do in Vienna?

What plant did Mendel mainly work

with?

B

What did he discover about tall plants?

What did he discover about short

plants?

What resulted from crossing tall and

short plants?

How many plants did he use?

How many years did it take?

What was his first law called?

What was his second law called?

C

How many basis laws of heredity did he

uncover?

Did he become famous in his life?

Why (not)?

When did he die?





What happened in 1900?





Activity 1.4.2. Testing the text

Choose the correct option

1) Gregor Mendel was:

a) an English gardener who grew pea plants

b) an unknown Central European monk

c) an early 20th century Dutch biologist who carried out genetics

research

2) Which of the following statements is true about Mendel?

a) His discoveries concerning genetic inheritance were accepted by

the scientific community

b) He believed that genetic traits of parents would usually blend in

their children.

c) He made statistical analysis in his breeding experiments

3) Mendel believed that the traits of the pea plants are determined by

the:

a) hereditary units or factors from both parents

b) hereditary units or factors from one parent

c) health of the plant during the pollination

4) Mendel discovered that:

a) short plants produced only short offspring

b) tall plants produced only tall offspring

c) short plants produced both, tall and short offspring

5) Mendel's law of independent assortment states that:

a) each pair of genes is inherited independently of all other pairs.

b) each pair of genes is inherited dependently of all other pairs.

c) only a gene is inherited independently of all other



Lesson 2.2. Swimming with Mendel’s laws


Activity 2.1.1. Hot seats

One of you plays Mendel’s role. Ask “this” Mendel questions about his

findings.

Activity 2.1.2. Genetic world words

a) Warming up!

Find out 15 of 15 words were placed into the puzzle.

R H G E S G E Y T N H W K J P

D K N V T F P I J C E I W L U

O U I Q Q E A T H D T D B K R

U G R K Q R M R P N E O Q H E

W J P K T G O A N H R M K G T

W W S H J M F P G M O I Z Z Q

V J F Z O J P A E G Z N A L F

O R F S E E M I W Q Y A V I E

S U O G Y Z O M O H G N I D D

G M G S I S O T I M O T J I I

E E L D I K I J W C U T R N R

T L N S E S D K A F S Z E Z B

O I E E H R E C E S S I V E Y

I K H H H M B W E L T N I X H

U G X I N I C S P E R M V E L

CHROMOSOME DOMINANT EGG GAMETE GENE

HETEROZYGOUS HOMOZYGOUS HYBRID MEIOSIS

MITOSIS OFFSPRING PURE RECESSIVE SPERM TRAIT





b) Definition Team Game

Word Cards (SM): Look at the set of cards you have. Listen to the

teacher and match the sentences teacher reads out and look for the

suitable word from your set. When you found it hand up.

c) Genetic Terminology Crossword

Across Down

1 Opposite of recessive 2 Different form of a gene

4 Section of DNA 3 Opposite to pure-breeding

5 Rewriting DNA's message 4 Combination of alleles

7 The first cell 6 Proteins factory

9 Humans have 23 pairs 8 Appearance of an organism's trai

(10 of 10 words were placed into the puzzle). Created by Puzzlemaker at DiscoveryEducation.com





d) Fill in the gaps: choose the correct word

1. Gregor , the "father of genetics" (Mendel/Darwin)

2. The first generation is the offspring of a cross between

parents that are pure for a given trait.

(Hybrid/Heterozygous/Homozygous-pure)

3. The principle of and recessiviness. (blending/dominance)

4. The outward expression or appearance: (phenotype/genotype)

5. Cross that involves parents that differ in TWO traits.

(dihybrid cross/ Monohybrid cross)

6. The study of heredity: (heredity/genetics)

7. An alternate form of a gene: (allele/factor)

8. The Principle of Assortment (dependent/independent)

9. Having non identical alleles (not pure; ex. Aa):

(heterozygous/homozygous)

10. Having identical alleles (pure, ex. AA):

(heterozygous/homozygous)

11. Square used to determine probability and results of cross:

(Punnett/Mendel)

12.The allele that is masked or covered up by the dominant allele:

(recessive/dominant)

13. The genetic make-up or an organism (Tt):

(recessive/dominant)

14. A cross that involves ONE pair of contrasting traits:

(test cross/ dihybrid cross)

15. The plants Mendel did his studies on:

(pea plants/peas plants)

16. The likelihood that an event will happen:

(probability/chance)

17. When neither allele is dominant (they are both expressed):

(codominant/recessiviness)

18. Principle of states that alleles separate when gametes are

formed.(segregation/separation)





Activity 2.2.1. Simple Genetics Practice Exercises

1. For each genotype, indicate whether it is heterozygous (HE) or

homozygous (HO)

AA

Bb

Cc

Dd

Ee

ff

GG

HH

Ii

Jj

kk

Ll

Mm

nn

OO

Pp

2. For each of the genotypes below, determine the phenotype.

Purple flowers are dominant to white

flowers

PP ____________

Pp ____________

pp ____________

Brown eyes are dominant to blue eyes

BB ___________

Bb ___________

bb ___________

Round seeds are dominant to wrinkled

RR ____________

Rr ____________

rr ____________

Short tails are recessive

(long tails dominant)

TT _______________

Tt _______________

tt ________________

3. For each phenotype, list the genotypes. (Remember to use the letter of

the dominant trait)

Straight hair is dominant to curly.

_______ straight

_______ straight

_______ curly

Pointed heads are dominant to round

heads.

________ pointed

________ pointed

________ round





4. Set up the square for each of the crosses listed below. The trait being

studied is round seeds (dominant) and wrinkled seeds (recessive)

Rr x rr

What percentage of the

offspring will be round?

Rr x Rr



RR x Rr



Practice with Crosses.

5. A TT (tall) plant is crossed with a tt (short plant).What percentage of

the offspring will be tall?

6. A Tt plant is crossed with a Tt plant. What percentage of the

offspring will be short?

7. A heterozygous round seeded plant (Rr) is crossed with a homozygous

round seeded plant (RR). What percentage of the offspring will be

homozygous (RR)?

8. A homozygous round seeded plant is crossed with a homozygous wrinkled

seeded plant. What are the genotypes of the parents?

What percentage of the offspring will also be homozygous?





9. In pea plants purple flowers are dominant to white flowers. If two white

flowered plants are crossed, what percentage of their offspring will be

white flowered?

10. A white flowered plant is crossed with a plant that is heterozygous for

the trait. What percentage of the offspring will have purple flowers?

11. Two plants, both heterozygous for the gene that controls flower colour

are crossed. What percentage of their offspring will have purple

flowers?

What percentage will have white flowers?

12. In guinea pigs, the allele for short hair is dominant. What genotype

would a heterozygous short haired guinea pig have?

What genotype would a pure breeding short haired guinea pig have?

What genotype would a long haired guinea pig have?

13. Show the cross for a pure breeding short haired guinea pig and a long

haired guinea pig





What percentage of the offspring will have short hair?

14. Show the cross for two heterozygous guinea pigs.

What percentage of the offspring will have short hair?

What percentage of the offspring will have long hair?

15. Two short haired guinea pigs are mated several times. Out of 100

offspring, 25 of them have long hair. What are the probable genotypes

of the parents? ___ x ___ Show the cross to prove it!





Activity 2.2.2. Two traits genetics crosses

In rabbits, grey hair is dominant to white hair. Also in

rabbits, black eyes are dominant to red eyes

These letters represent the

genotypes of the rabbits:

1. What are the phenotypes (descriptions) of rabbits that have the

following genotypes?

Ggbb _________________ ggBB ______________________

ggbb _________________ GgBb ______________________

2. A male rabbit with the genotype GGbb is crossed with a female rabbit

with the genotype ggBb the square is set up below. Fill it out and

determine the phenotypes and proportions in the offspring.

Gb Gb Gb Gb

gB

gB

gb

gb

How many out of 16 have grey fur and black eyes?

How many out of 16 have grey fur and red eyes?

How many out of 16 have white fur and black eyes?

GG = grey hair

Gg = grey hair

gg = white hair

BB = black eyes

Bb = black eyes

bb = red eyes





How many out of 16 have white fur and red eyes?





3. A male rabbit has the genotype GgBb. Determine the gametes produced

by this rabbit (the sperm would have these combinations of alleles) Hint:

there are 4 combinations.

4. A female rabbit has the genotype ggBb. Determine the gamets (eggs)

produced by this rabbit.

5. Use the gametes from 4 and 5 to set up the punnet square below. Put

the female's gametes on the top and the male's gametes down the side.

Then fill out the square and determine what kind of offspring would be

produced from this cross and in what proportion.

gB gb

GB

Gb

gB

gb



Lesson 2.3. Swinging with Mendel’s laws exceptions


Activity 2.3.1

Co-dominance, Intermediate Expression and Multiple Allele

� If there are only two alleles involved in determining the phenotype of a

certain trait, but there are three possible phenotypes, then the

inheritance of the trait illustrates either incomplete dominance or codominance. The incomplete dominance is also known as intermediate

expression, and the phenotype is shown as a blend of the parental

phenotypes. Codominance phenotype shows both traits, ie. From a black

and white, the offspring phenotype is black with white spots.

1. Practice setting up keys for the phenotypes listed in each set. Remember

that the "medium" trait must always be heterozygous.

a) Birds can be blue, white, or white with dark-blue feathers.

b) Flowers can be white, pink, or red.

c) A can have curly hair, spiked hair, or a mix of both curly and spiked.

d) A can be tall, medium, or short.

e) A can be spotted, black, or white.





2. Now, can you figure out in the above list, which of the examples

represent codominant traits and which are incomplete.

� When there are 4 or more possible phenotypes for a trait, then more

than 2 alleles for that trait must exist in the population but individuals

have only two of those alleles. That happens because individuals have

only two biological parents. We inherit half of our genes (alleles) from

the mother and the other half from the father, so we cannot have

more tan two alleles for every trait in our phenotype. An example of

multiple allele inheritance is human blood type. Blood type exists as

four possible phenotypes: A, B, AB, and O. there are 3 alleles for the

gene that determines blood type. The allele for O (i) is recessive to

the alleles for A and B. The alleles for A and B are codominant. The

alleles are noted as i, IA and IB

3. Mrs. Drinkwater is blood type A and her mother is 0. Her children are

o, B and A. Find out what Mr Drinkwater’s blood group could be.





Activity 2.2.3. Genetics of Sex Determination

� In humans the genetic determination of sexual identity involves

chromosomes. Humans have 46 chromosomes, 44 of these chromosomes pair

together to make 22 pairs of homologous chromosomes (autosomes); the

other 2 chromosomes are different, because they are involved in determining

the sex. They are called sex chromosomes (XX/XY). Males have an X and a Y

chromosome (XY), and females have two X chromosomes (XX). It is known

that it is the presence of the Y chromosome that makes the individual male.

Your knowledge of meiosis and fertilization provides the basis for

understanding the inheritance of X and Y chromosomes. During meiosis in a

female, the two X-chromosomes separate, so each egg has a single X-

chromosome. In males, even though the X and the Y-chromosomes are very

different, they can nevertheless pair with each other and separate from

each other during meiosis. This means that males produce two kinds of

sperm; half have an X chromosome and half have a Y chromosome.

a) What will be the sex of a child produced when an egg is fertilized by a

sperm that has a Y chromosome?

What type of sperm must fertilize an egg to result in a female child?

b) Draw a Punnett Square which shows the inheritance of the sex

chromosomes. Use X to indicate an egg or sperm with an X chromosome

and Y to indicate a sperm with a Y chromosome.





c) Based on this Punnett Square, what percent of children would you expect

to be male?



Lesson 2.4. Let’s have children!...and something else


Activity 2.2.4. Sex-linked Traits

� In humans, the X chromosome carries some genes that are not found in the Y

chromosome. Inheritance of the phenotypic traits determined by the genes

located in these chromosomes is therefore linked to the sex of the person.

The X chromosome carries other genes which are not associated with

determination of sex. One of these genes codes for a protein called blood

clotting factor. Mutations can occur in this gene resulting in a blood protein

that cannot clot the blood properly. This disease is known as haemophilia.

Haemophilia Notation: XH chromosome with normal clot factor and Xh

In humans, haemophilia is a sex linked trait. Females can be normal, carriers, or

have the disease.

Males will either have the disease or not (but they won’t ever be carriers)

Female normal: XHXH

Female carrier: XhX

Female haemophiliac: XhXh

Male normal: XY

Male haemophiliac: XhY

Show the cross of a man who has haemophilia with a woman who is a

carrier. Draw the cross in the Punnett square.





What is the probability that their children will have the disease?

A woman who is a carrier marries a normal man. Show the cross. What is

the probability that their children will have haemophilia?

What sex will a child in the family with haemophilia be?

A woman who has haemophilia marries a normal man. How many of their

children will have haemophilia, and what is their sex?





Activity 2.4.1.

LET’S HAVE CHILDREN!

What will our children look like?

� Your teacher will give you an envelope with a set of 4 X 2

chromosomes. The chromosomes are in different colours and present

different alleles.

� Look at the chromosomes you have and fill in the chart with your

phenotype and genotype.

� Simulate meiosis by tossing a coin. If heads, take chromosome X, if

tails chromosome X‘.

� Now work with your partner and take your simple chromosome and

match it with your partner’s simple chromosome. You both have your

first child.

� Read and write your child’s phenotype and genotype. Repeat the

process three or four more times.

Activity 2.4.2. Genetic Report

Work in groups of 3-4 students. Each group should write a genetic

report for the Drinkwater family.

Find out the information needed and write it down in the table.





Mr & Mrs. Drinkwater: Genetic Report Part I: The Drinkwater Family’s pedigree.

Part II: The Drinkwater Family's Haemophilia

Part III: Information about Haemophilia

To finish the report:

You will be divided into two groups: the Drinkwaters and the

Geneticists.





Your aim is to answer Mrs Drinkwater’s question.

(Key: As “geneticists and applying all you know about genetics find out

possible solutions to have a child not suffering from haemophilia in order to

tell the Drinkwaters)

Final activity Role Play game: Let’s discuss!

You will be divided into two groups to discuss the use of biotechnology

in society, the ethical/moral implications of their use, etc…

One group is FOR the use of biotechnology, the other AGAINST.

First, work in your group to decide on why you are for or against

(remember, these don’t have to be your real opinions). Make some notes.

Now, as a whole class, you will have a debate. Do not be afraid to express

your opinion and try to argue or justify it.

Each group will choose a secretary which will summarize your opinions.

When the discussion is over write them in the Venn Diagram below:

introduction to genetics - xtec to genetics from proteins to mendel student worksheets unit 1 lesson...

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