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