chapter 4: chapter 4: patterns of heredity section 1: living things inherit traits in patterns
TRANSCRIPT
Chapter 4Chapter 4:: Patterns of
HereditySection 1Section 1: Living : Living
things inherit traits in things inherit traits in patterns.patterns.
Inherited TraitsInherited TraitsTraits passed down from Traits passed down from your parentsyour parents
Genetically linkedGenetically linked
Acquired TraitsAcquired Traits Something gained or learn Something gained or learn
during your lifetimeduring your lifetime
Not genetically linkedNot genetically linked
Acquired Acquired traitstraits
Inherited Inherited TraitsTraits
CombinatioCombination of Bothn of Both
Learning to SnapLearning to Snap Eye colorEye color DiabetesDiabetes
HeredityHeredity
is the passing of genes from parents to offspring These genes code for the expression
of traits. an organism does not inherit the traits
ONLY the genes for the traits Some characteristics are affected by
many genes in complicated ways.
HomologsHomologs Most eukaryotic cells
contain pairs of chromosomes, with one chromosome of each pair coming from each of two parents.
The chromosomes in a pair are called homologs. They resemble each other,
having the same size and shape, and carrying genetic information for particular traits.
alleles
a gene
AllelesAlleles
An alternate form of a gene for a specific trait or gene product. Ex) in the picture A
or a are different alleles for the same gene
Ex) Tongue roller and non-tongue roller are different alleles for people
alleles
a gene
GeneGene
The basic unit of heredity that consists of a segment of DNA on a chromosome.
Are sites that code for particular traits such as eye color, hair color, etc.
alleles
a gene
Each species has a Each species has a characteristic number of characteristic number of
chromosomes.chromosomes. Chimpanzees have 24 Chimpanzees have 24
pairs of chromosomes pairs of chromosomes (48 total)(48 total)
Fruit flies have 4 pairs Fruit flies have 4 pairs of chromosomes (8 total) of chromosomes (8 total)
Humans have 23 pairs Humans have 23 pairs (46 total)(46 total)
What’s special about the 23What’s special about the 23rdrd pair?pair?
The 23rd pair are the sex chromosomes.
In humans, the sex chromosomes are called the X-chromosome and the Y-chromosome.
A human female = XX
A human male = XY
Phenotype vs. GenotypePhenotype vs. Genotype Describes the
actual characteristics that can be observed
P for Picture of what the genes “look” like
Ex.) Brown hair, Blue eyes
The name for the genes an organism has.
Describe an organisms specific alleles
Ex.) Aa, AA, aa
Dominant vs. RecessiveDominant vs. Recessive More prominent, More prominent,
more powerful, more powerful, stronger allelesstronger alleles
Usually represented Usually represented by a by a capital lettercapital letter
Only needs Only needs 1 allele1 allele to control the to control the phenotypephenotype
Has the power to Has the power to mask (hide) mask (hide) recessive allelesrecessive alleles
Less prominent, Less prominent, less powerful, less powerful, weaker allelesweaker alleles
Usually represented Usually represented by a by a lower case lower case letterletter
Needs Needs 2 alleles2 alleles to to control the control the phenotypephenotype
Can not mask Can not mask dominant alleles dominant alleles
Homozygous vs. Homozygous vs. HeterozygousHeterozygous
Having 2 of the Having 2 of the same alleles in same alleles in the genotypethe genotype BB – Homozygous BB – Homozygous
Dominant Dominant bb – Homozygous bb – Homozygous
recessiverecessive
Also known as a Also known as a PURE BREEDPURE BREED
Having 2 Having 2 different alleles different alleles in the genotypein the genotype Bb – Bb –
HeterozygousHeterozygous
Also known as Also known as a a HYBRIDHYBRID
Gregor MendelGregor Mendel A monk, trained in science and math,
who lived in Austria during the mid- 1800s
Performed the first major experiments investigating heredity
Began investigating the inheritance of traits among the pea plants in the his garden
Separately worked with seven different traits: plant height flower and pod position,
seed shape, seed color, pod shape, pod color, and flower color.
Mendel Experiments Mendel noticed
variations in the heights of pea plants
So he purposely crossed (mated) pea plants that were pure-breed dwarf & pure-breed regular to see what their offspring would become
Regular x Dwarf
T T x t t
First generation (F1 )
After crossing a true-breeding regular pea plant with a true-breeding dwarf pea plant all regular pea plants were
produced in the first generation.
Two of these plants were then crossed to produce a second generation
F1 generation all regular (Tt)
Second generation (F2 )
After allowing the first generation pea plants to cross
¾ regular pea plants (TT & Tt) and ¼ dwarf pea (tt) plants were produced
1 Regular (TT), 2 Regular (Tt), & 1 Dwarf (tt)
were produced
So What?!?So What?!?
Mendel drew upon his knowledge of mathematics while analyzing his data in order to suggest a hypothesis that would explain the patterns he observed.Mendel realized that each plant must have two “factors” for each possible trait, one factor from each parent. Some traits, such as dwarf height, could be masked—dwarf height could be seen in the
Chapter 4Chapter 4:: Patterns of
HereditySection 2Section 2: Patterns of : Patterns of
heredity can be heredity can be predictedpredicted
Punnett SquarePunnett Square
Illustrates how the Illustrates how the parent’s genes can parent’s genes can possibly combinepossibly combine
RatioRatioCompare 2 different Compare 2 different quantities (numbers)quantities (numbers)Ex) Ratio of boys to girls Ex) Ratio of boys to girls = 10 to 7 or 10:7= 10 to 7 or 10:7
# order depends on the # order depends on the wordingwording
ProbabilityProbabilityThe chance or The chance or likelihood of an event likelihood of an event or something or something happeninghappening
PercentagePercentageCompares the Compares the probability of probability of something to 100something to 100Ex) 93% of the questions Ex) 93% of the questions on a test were correcton a test were correct
Incomplete dominanceIncomplete dominance
Also known as “Co-Also known as “Co-dominance”dominance”
Is when there are 2 different Is when there are 2 different dominant alleles which dominant alleles which share powershare powerEx) RW = pink in poinsettiasEx) RW = pink in poinsettias
Dihybrid CrossesDihybrid Crosses Deals with 2 genotypes at Deals with 2 genotypes at
onceonce Includes 4 allelesIncludes 4 alleles
Brown Hair = BBrown Hair = BBlonde Hair = bBlonde Hair = bBrown eyes = QBrown eyes = QBlue eyes qBlue eyes q
BBQQBBQQ BBQqBBQq BbQQBbQQ BbQqBbQq
BBQqBBQq BBqqBBqq BbQqBbQq BbqqBbqq
BbQQBbQQ BbQqBbQq bbQQbbQQ bbQqbbQq
BbQqBbQq BbqqBbqq bbQqbbQq bbqqbbqq
BQ Bq bQ bq
BQ
Bq
bQ
bq
GenoGeno BBQBBQQQ
BBQqBBQq BbQQBbQQ BbQqBbQq BBqqBBqq BbqqBbqq bbQQbbQQ bbQqbbQq bbqqbbqq
PhenoPheno Br Br hair hair & & eyes eyes
Br Br hair & hair & eyeseyes
Br Br hair & hair & eyeseyes
Br Br hair & hair & eyeseyes
Br Br hair & hair & blue blue eyeseyes
Br Br hair & hair & blue blue eyeseyes
BlondBlonde & br e & br eyeseyes
BlondBlonde & br e & br eyeseyes
BlondBlonde & e & blue blue eyeseyes
pp
Br & Br & brbr
9/169/16
Br & Br & blbl
3/163/16
Bl & Bl & brbr
3/163/16
Bl & Bl & blbl
1/161/16
Chapter 4Chapter 4:: Patterns of
HereditySection 4.3: Meiosis is a Section 4.3: Meiosis is a
special form of cell divisionspecial form of cell division
GameteGamete Special cells that contain only Special cells that contain only
half the number of chromosomes half the number of chromosomes in a normal cell of that organismin a normal cell of that organism
Also known as “1n” cells, haploid Also known as “1n” cells, haploid or sex cells or sex cells In a female their gametes are In a female their gametes are
referred to as eggsreferred to as eggs In males, gametes are referred to In males, gametes are referred to
as spermas sperm
Body CellsBody Cells Are normal typical cellsAre normal typical cells
Ex) skin, or muscle cellsEx) skin, or muscle cellsAlso known as “2n cells” or Also known as “2n cells” or diploid cellsdiploid cells
FertilizationFertilization
The process The process that takes that takes place when the place when the egg and the egg and the sperm combine sperm combine to form one to form one new “2n cell”new “2n cell”
MeiosisMeiosisSpecial kind of cell division Special kind of cell division that produces haploid cellsthat produces haploid cells
Involves a single cell going Involves a single cell going through 2 divisions through 2 divisions Meiosis I & Meiosis IIMeiosis I & Meiosis II
• At the beginning of meiosis I, the parent cell has made two copies of each chromosome pair.
• During meiosis I, the homologs of the chromosome pair separate; there are two cells, each with two copies of one homolog from each pair.• During meiosis II, the two copies of each homolog separate; each daughter cell has one homolog.
Meiosis II
1n
1n
1n
1nMeiosis I
How meiosis works…How meiosis works…
MitosisMitosis MeiosisMeiosis
Produces 4 Produces 4 daughter daughter cellscells
Splits twiceSplits twice Daughter Daughter
cells have ½ cells have ½ the parents the parents genetic info genetic info (DNA)(DNA)
Produces 1n Produces 1n cell, haploid cell, haploid cells, gamete cells, gamete or sex cellsor sex cells
Has 8 main Has 8 main stagesstages
Starts with Starts with a single cella single cell
Are forms of Are forms of cell divisioncell division
Happens in Happens in stagesstages
ChromosomeChromosomes (DNA) only s (DNA) only copied 1 copied 1 timetime
Produces 2 Produces 2 daughter daughter cellscells
Splits onceSplits once Parent and Parent and
daughter daughter cells cells genetically genetically identicalidentical
Produces 2n Produces 2n cell, diploid cell, diploid cells or body cells or body cellscells
Has 4 main Has 4 main stagesstages