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Heredity (Inheritance) and Genetics. Heredity. Is it possible for two parents with blue eyes to have a brown eyed child?. Heredity. 2. Is it possible for two parents with brown eyes to have a blue-eyed child?. Heredity.

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heredity
Heredity
  • Is it possible for two parents with blue eyes to have a brown eyed child?
heredity1
Heredity

2. Is it possible for two parents with brown eyes to have a blue-eyed child?

heredity2
Heredity
  • Rebecca and Leah look so much alike that everyone says they must be sisters. What kind of test should we do to determine if they are sisters?
review
Review

What do you know about each of the following:

  • DNA
  • Genes
  • Chromosomes
chromosomes have genetic information and are passed to offspring
Chromosomes have genetic information and are passed to offspring

Dividing onion cells

chromosomes

chromosomes

cell wall

nucelus

chromosomes have genetic information and are passed to offspring1
Chromosomes have genetic information and are passed to offspring

Human chromosomes stained with a special chemical and viewed under a high-powered microscope

slide8
What exactly are chromosomes?

How do chromosomes contain genetic information?

chromosome structure dna
Chromosome structure- DNA
  • Chromosomes = long pieces of DNA
chromosome structure genes
Chromosome structure- genes
  • Parts of chromosomes are called genes
  • Genes help determine your characteristics
    • what are some example characteristics?

Human chromosome # 7

  • Contains about 1,800 genes
  • Contains over 150 million nucleotides

Link to view genes and DNA sequence

slide11
Trait – a characteristic of an organism
  • Example: “flower color”

Gene – part of a chromosome that helps determine a specific trait

  • Example: “flower color gene”

Allele – a form of a gene

  • Example:
    • One allele is the “blue” form of the gene
    • One allele is the “red” form of the gene
review1
Review

How do the terms trait, chromosome, gene, and allele relate to each other?

chromosomes come in pairs
Chromosomes come in pairs

Cut out from picture and

match each in pairs. This is called a KARYOTYPE

homologous chromosomes
Homologous chromosomes?
  • Humans = 23 chromosome pairs, or 46 total. We think we have about 20,000 genes.
  • Pea flower = 7 chromosome pairs (14 total)
  • Fruit fly = 4 chromosome pairs (8 total) 13,601 genes identified so far!
    • What part of a chromosome do you think is homologous or identical?
    • What effect do these differences have on characteristics?
chromosomes come in pairs1
Chromosomes come in pairs
  • You get one copy of a chromosome from one parent and one copy of a chromosome from the other parent.
  • This pair of chromosomes is called a “homologous pair” because they have the same genes on them -

flower color gene

Flower chromosome 3

From Dad

From Mom

chromosomes come in pairs2
Chromosomes come in pairs

IMPORTANT: homologous pairs have the same genes, but they are NOT IDENTICAL

  • Alleles can be different

flower color gene

“Blue” allele

of flower color

gene

“Red” allele

of flower color

gene

From Dad

From Mom

chromosomes are shuffled
Chromosomes are shuffled

When homologous chromosomes are reunited following meiosis and sex, the combination of Alleles can be different

flower color gene

“Blue” allele

of flower color

gene

“Red” allele

of flower color

gene

From Dad

From Mom

the combination of alleles determines the observed characteristics
The combination of alleles determines the observed characteristics

RED

allele

BLUE

allele

RED

allele

BLUE

allele

BLUE

allele

RED

allele

Chromosome

combination

Allele

combination

red, red

red, blue

(or blue, red)

blue, blue

Observed

characteristic

RED

?

BLUE

dominant and recessive alleles
Dominant and recessive alleles

Only one red allele is needed for the flower to look red.

  • Scientists call this a DOMINANT allele

Two blue alleles are needed for the flower to look blue.

  • Scientists call this a RECESSIVE allele
symbols used for alleles
Symbols used for alleles
  • The traditional symbols used for alleles are big and small letters
  • The letter chosen usually refers to the dominant allele

Example: R = Red allele

r = Blue allele

the combination of alleles determines the observed characteristics1
The combination of alleles determines the observed characteristics

RED

allele

BLUE

allele

RED

allele

BLUE

allele

BLUE

allele

RED

allele

Chromosome

combination

Allele

combination

red, red

red, blue

(or blue, red)

blue, blue

Observed

characteristic

RED

RED

BLUE

the combination of alleles determines the observed characteristics2
The combination of alleles determines the observed characteristics

R

R

R

r

r

r

Chromosome

combination

Allele

combination

RR

Rr

rr

Observed

characteristic

RED

RED

BLUE

slide23
Phenotype – the observed (or measurable) trait of an organism that relates to one gene

Genotype – the two alleles that an organism has for a trait

Example: Trait = “flower color”

Phenotype = “RED” or “BLUE”

Genotype = “RR” or “Rr” or “rr”

the combination of alleles determines the observed characteristics3
The combination of alleles determines the observed characteristics

R

R

R

r

r

r

Chromosome

combination

Allele

combination

RR

Rr

rr

Observed

characteristic

RED

RED

BLUE

the combination of alleles determines the observed characteristics4
The combination of alleles determines the observed characteristics

R

R

R

r

r

r

Chromosome

combination

GENOTYPE

RR

Rr

rr

PHENOTYPE

RED

RED

BLUE

slide26
Homozygous – the two alleles are the same
  • RR and rr are homozygous genotypes

Heterozygous – the two alleles are different

  • Rr is a heterozygous genotype
review2
Review
  • What are homologous chromosomes?
  • What part of a chromosome do you think is homologous or identical.
  • What is a dominant allele?
  • What is a recessive allele?
  • What is homozygous?
  • What is heterozygous?
  • What is phenotype?
  • What is genotype?
modeling genetic crosses
Modeling Genetic crosses
  • Documents and Models how genetic information is passed along.
  • Accounts for patterns seen in a pedigree
  • Makes predictions about the phenotypes and genotypes seen in the next generation
possible combinations of inherited chromosomes genes
Possible combinations of inherited chromosomes/genes

Dad

Mom

Parents

R r

R r

X

R

R

Possible

Offspring

Order doesn’t matter,

these two are the same (Rr)

R

r

r

R

r

r

What are all possible genotypes produced from the parents?

RR, Rr, rr

punnett squares organize all possible offspring combinations
Punnett squares organize all possible offspring combinations

Dad

Mom

R r

R r

X

Your turn:

What are all possible genotypes produced by crossing Rr with rr?

R

r

R

RR

Rr

r

Rr

rr

punnett squares predict ratios of all genotypes and phenotypes produced
Punnett squares predict ratios of all genotypes and phenotypes produced

Genotypic ratio =

Phenotypic ratio =

1RR: 2Rr:1rr or 25%RR:50%Rr:25%rr

3 Red:1 blue or 75% Red:25% Blue

predicted ratios determine the probability of each genotype phenotype
Predicted ratios determine the probability of each genotype/phenotype

1 out of 4 possibilities is rr = 25% chance of rr

  • What is probability of Rr?
  • How many out of 4 are red?
  • What is the probability of red?
  • What is the probability of blue?

Genotypic ratio = 1RR: 2Rr:1rr

Phenotypic ratio = 3 Red:1 blue

punnett square practice
Punnett square practice

Calculate the predicted genotypic and phenotypic ratios

Calculate the probability of each genotype and phenotype

  • Hh X HH – H(hairy) is dominant over h(not hairy)
  • Gg X gg – G(green sepals) is dominant over g(yellow sepals)
review3
Review
  • What is the relationship between genotype and phenotype?
  • What is the relationship between Homozygous and Heterozygous
  • Give an example of a heterozygous genotype for height (T = tall; t = short):
  • Give an example of a homozygous genotype for height (T = tall; t = short):
  • What is the phenotype of a plant heterozygous for the height gene?
dihybrid cross
Dihybrid cross
  • Used to predict the combinations of 2 traits contained on two separate chromosomes.
  • For example for the traits of stripes and tails on a cat:
    • Two double-heterozygous striped, with tail cats are crossed.
    • How many offspring will be striped and have a tail, how many will be striped with no tail, how many will be plain with a tail…
practice
Practice
  • Construct a Punnett Square for each of the following crosses.
  • Remember: the two traits are on two different chromosomes.
  • Write the Genotypic and Phenotypic Ratio below the Punnett Squares.
  • SsTt X SsTt
  • SSTt X SsTt
  • SSTT X SsTt

S = striped

s = plain

T = tail

t = no tail

sstt x sstt
SsTt X SsTt

S = striped

s = plain

T = tail

t = no tail

sstt x sstt1
SsTt X SsTt

S = striped

s = plain

T = tail

t = no tail

sstt x sstt2
SsTt X SsTt

S = striped

s = plain

T = tail

t = no tail

sstt x sstt3
SsTt X SsTt

S = striped

s = plain

T = tail

t = no tail

sstt x sstt4
SsTt X SsTt

S = striped

s = plain

T = tail

t = no tail

sstt x sstt5
SsTt X SsTt

S = striped

s = plain

T = tail

t = no tail

Genotypes: 1 SSTT: 2 SSTt: 1 SStt: 2 SsTT: 4 SsTt: 2 Sstt: 1 ssTT: 2 ssTt: 1 sstt

Phenotypes: 9 striped, tail : 3 striped, no tail : 3 plain, tail : 1 plain, no tail

sstt x sstt6
SSTt X SsTt

S = striped

s = plain

T = tail

t = no tail

If they are the same as above you do NOT have to rewrite the genotype

Genotypes: 1 SSTT: 1SSTt: 1SsTT: 1SsTt: 1SSTt: 1SStt: 1SsTt: 1Sstt

Phenotypes: 6 Striped with Tail: 2 Striped with no tail (3:1 reduced)

sstt x sstt7
SSTT X SsTt

S = striped

s = plain

T = tail

t = no tail

Same

Genotypes: 1 SSTT: 1 SSTt: 1 SsTT: 1 SsTt

Phenotypes: 4 Striped Tail (100%)

slide46

#1 #2 #3

#1 #2 #3

  • What is the trait for the flowers? __________________
  • What is the trait for the animals? __________________
  • What is the recessive allele for the flower trait? _______
  • What is the dominant allele for the animal trait? _______
  • Which flower is heterozygous? ___________
  • Which animal is homozygous dominant? __________
  • What is the genotype of flower #1? ________________
  • What is the genotype of animal #2? ________________
  • What is the phenotype of flower #2? ________________
  • What is the phenotype of animal #3? ________________

Width/thickness/petals

Type of Hair

f (or narrow)

H (or straight)

#1

#2

Ff

HH

Wide

Straight Hair

punnett square
Punnett Square

F f

Genotypic ratio:

Phenotypic ratio:

1 Ff : 1 ff

(2 Ff : 2 ff is OK)

f

f

Ff ff

1 fat : 1 skinny

(2 fat : 2 skinny is OK)

Ff ff

review4
Review

In flowers, red color (R) is dominant to blue color (r).

  • What possible genotypes produce a blue flower? What possible genotypes produce a red flower?
  • Explain how you could determine the actual genotype of a red flower by performing a genetic cross many times and looking at the offspring phenotypes.
review5
Review
  • How many sets of your 23 chromosomes do you have (1, 2, 3, or 4?)
  • How many of each type of chromosome is inherited from your mom?
  • How many of each type of chromosome is inherited from your dad?
if parents have two copies of each chromosome how do they pass on only one to their offspring

Original cell

Sperm or egg cells

If parents have two copies of each chromosome, how do they pass on only one to their offspring?
  • MEIOSIS is the process of cell division that decreases the number of chromosomes to make sperm or egg cells
the purposes of meiosis
The purposes of Meiosis:
  • Split the total number of chromosomes in half so that only ONE chromosome from each pair is inherited from each parent.
  • Produce variation in offspring by randomly sorting the chromosomes.
meiosis
Meiosis
  • Original cell
  • Diploid
    • (pairs of chromosomes)
  • Sperm or egg cells
  • Haploid
    • (single chromosomes)
fertilization
Fertilization

Sperm

Egg

Gametes:

(haploid sex cells)

Zygote:

(diploid embryo)

Fertilized egg