introduction to genetics. learning targets i can define and provide an example of the following:...

Introduction to Genetics

Learning Targets

I can define and provide an example of the following: genotype, phenotype, dominant allele, codominant alleles, incompletely dominant alleles, homozygous, heterozygous, and carrier.

Genetics Terms

Heredity is the passing of traits from parents to offspring

Traits are inherited characteristics such as eye color, height, hair color

Fertilization is the uniting of male and female gametes

Pollination is plant fertilization

More Terms

Gametes-specialized cells involved in sexual reproduction; sperm or egg; pollen or ovum

Gene-sequence of DNA that codes for a protein and thus determines a trait

Probability-likelihood that a particular event will occur

More terms

Alleles are the various genes for the same trait

Dominant traits are those that are always expressed when present (brown eyes)

Recessive traits are only expressed if the dominant trait is absent (blue eyes)

More terms

Homozygous means possessing a pair of identical alleles for a trait; can be dominant or recessive. Shown by AA or aa

Heterozygous means possessing a pair of unlike alleles; dominant trait is expressed; recessive trait is carried; Aa

More Terms

Phenotype is the physical appearance of a trait

Genotype is the actual genetic makeup; XX for females; XY for males

Even more terms

True breeders -organisms that produce offspring identical to themselves if allowed to self-pollinate

Hybrids – offspring of crosses between parents with different traits

Learning Targets

I can define and provide an example of the following: genotype, phenotype, dominant allele, codominant alleles, incompletely dominant alleles, homozygous, heterozygous, and carrier.

Gregor Mendel

http://science.discovery.com/tv-shows/greatest-discoveries/videos/100-greatest-discoveries-shorts-genetics.htm

Gregor Mendel

Father of genetics Born 1822 on farm in Austria (now Czech

Republic) Entered monastery in 1843

Mendel

Sent to University of Vienna; studied botany and other subjects

Became chief gardener at the monastery

Monks helped feed not only themselves but their community

Mendel

Mendel sought to increase production and yield of their crops

Mendel started breeding peas in 1857 to study inheritance

His study took 10 years to complete His methods are still used today

because he kept meticulous records

Why Peas?

• Many varieties have two clearly different traits Flower color Seed color Seed shape

• Plants are easy to control Male and female parts on same flower

(dioecious) Pollen is male ; ovule is female

Learning Targets

I can describe the basic mechanisms of plant processes, especially movement of materials and plant reproduction.

I can explain the functions of unique plant structures.

Flowers

http://www.youtube.com/watch?v=OpzvKdmAoI0

Parts of a Flower Sepals-outermost circle of floral parts; usually green and look like leaves

Petals-often brightly colored; found just inside the sepals

Leaf-photosynthetic organ that contains on or more Bundles of vascular tissue

Parts of a Flower Terms Stamen-male part of the flower; made of filament and anther

Filament-a long thin structure that supports the anther

Anther-flower structure in which haploid male gametes are produced

Parts of a Flower Terms

Pistils (Carpels)-innermost part of a flower that produces the female gametes Stigma- sticky portion at the top of the style where pollen grains land Style-narrow stalk of the carpel in a flower Ovary-a flower structure that contains one or more ovules from which the female gametes are made Ovule-female gamete

Vascular Tissue in Plants Xylem-vascular tissue that carries water

from the roots to the rest of the plant

Phloem-vascular tissue that transports nutrients and carbohydrates made by photosynthesis

Vascular Bundles-a plant stem structure that contains xylem and phloem tissue

Plant Life Cycle

Plant Fertilization

http://www.youtube.com/watch?v=LdlxUJhoyx4

Plant Fertilization

Learning Targets

I can describe the basic mechanisms of plant processes, especially movement of materials and plant reproduction.

I can explain the functions of unique plant structures.

Learning Targets

I can identify and explain Mendel’s laws of segregation and independent assortment

I can construct and interpret Punnett squares (calculating and predicting phenotypic and genotypic ratios of offspring)

Mendel’s Procedure

1. Remove immature stamen from plant2. Took brush and removed pollen from

one plant3. Then brushed pollen onto ova of

another plant4. Allowed plant to seed and then

planted the seeds

Mendel’s Peas

Studied over 30,000 plants in 10 years

Usually followed his plants for 3 generations

Studied flower color, seed color, seed shape, height

Always started with true breeders

Covered plants to keep pollinators away

Mendel’s Peas

Began by crossing tall & short plants Expected an intermediate height plant Instead all plants were tall Let these plants self pollinate and got

3:1 ratio Three tall plants to every short plant He decided that each trait had at least

two factors for each trait; called these alleles

Probability and Punnett Squares

The principles of probability can be used to predict the outcomes of genetic crosses.

Flipping a coin 50/50 chance of getting a head every

time

Punnett Squares

A diagram used to predict genetic probabilities

Can compare genetic variations that will result from a specific cross

Monohybrid Crosses

A monohybrid cross occurs between two parents that breed true for different versions of a single trait

Allows tracking of one trait only

Monohybrid Cross

Tt Tt

Tt Tt

P Generation

T T

t

t

All were tall

Monohybrid Cross

TTTt

Tt tt

F1 Cross

T tT

t

Phenotype: 3:1

Genotype: 1:2:1

Rule of Dominance

To be dominant, an organism must possess either two dominant alleles or at least one dominant allele

To be recessive, the organism must receive two recessive alleles; one from each parent

Principle of Segregation

Pairs of alleles separate during gamete formation in meiosis.

The fusion of gametes pairs the alleles again at fertilization

Principle of Independent Assortment

Each pair of alleles separates independently of each other during gamete formation

Incomplete Dominance

Rr Rr

Rr Rr

Snap Dragons

Red crossed with White

Expected 3:1 ratio Red to White

R R

r

r

Got all PINK!

Codominance

The expression of two different alleles in a heterozygote

Many genes have different alleles; but usually only two or less are expressed in the individual

Blood is expressed in different alleles: A, B, AB or O

A and B are dominant; O recessive AB is codominant

Dihybrid Crosses

A cross where two traits are examined

Predicts two different traits Parents will have four possible

gametes displaying the various combinations of the two traits

Mendel used seed shape and seed color for one of his dihybrid crosses

Dihybrid Cross

RRYY x rryy

R = round Y = Yellow r = wrinkled y=green

Dihybrid Parent Cross

RY RY RY RY

ry RrYy RrYy RrYy RrYy

ry RrYy RrYy RrYy RrYy

ry RrYy RrYy RrYy RrYy

ry RrYy RrYy RrYy RrYy

Dihybrid Cross

Crossing pure breeding homozygous dominant with pure breeding homozygous recessive

RRYY X rryy All offspring are heterozygous for the

trait RrYy

Dihybrid F1 Cross

RY rY Ry ry

RY RRYY RrYY RRYy RrYy

rY RrYY rrYY RrYy rrYy

Ry RRYy RrYy Rryy Rryy

ry RrYy rrYy Rryy rryy

F1 Generation Dihybrid Cross

Allowing F1 to cross pollinate results in a 9:3:3:1 ratio

9 will be round, yellow 3 will be round, green 3 will be wrinkled, yellow 1 will be wrinkled, green

Learning Targets

I can identify and explain Mendel’s laws of segregation and independent assortment

I can construct and interpret Punnett squares (calculating and predicting phenotypic and genotypic ratios of offspring)