homework practice genetics wrong I need

Consider an organism that has three pairs of chromosomes. At the start of meiosis Il, each cell would have chromosomes and

chromatids.

six; three

three; six

three; three

six; six

three; six

“Three PAIRS of chromosomes"

A pair means 2 chromosomes.

So:

3 pairs × 2 = 6 chromosomes

So it's a diploid organism with 6 chromosomes total, and a haploid cell has 3 chromosomes.

What are the sex chromosomes for HUMANS?

XY XX

XO XX

ZZ ZW

haploid diploid

XY XX

What are the sex chromosomes for BEES?

XY XX

XO XX

ZZ ZW

haploid diploid

haploid diploid

What are the sex chromosomes for BIRDS?

XY XX

XO XX

ZZ ZW

haploid diploid

ZZ ZW

What are the sex chromosomes for CRICKETS?

XY XX

XO XX

ZZ ZW

haploid diploid

XO XX

Two plants each have a gene that determines pea pod color. In one plant, this gene produces yellow pea pods. In the other plant, this gene produces green pea pods. What are these variations of pea pod genes called?

Gametes

Alleles

Zygotes

Hybrids

Alleles

• Gametes
  Reason: A gamete is a haploid reproductive cell.

• Alleles

• Zygotes
  Reason: A zygote is a diploid cell formed when two gametes fuse.

• Hybrids
  Reason: A hybrid is the offspring that results when two organisms with distinct characteristics are crossed.

A heterozygous genotype would contain two alleles for every gene under consideration.

mutant

dominant

recessive

different

wild-type

identical

different

Hetero = different

Zygous = allele combination

So: Heterozygous = having TWO DIFFERENT alleles for a gene.

The combination of alleles that an individual has is called its

genotype

An alternative form of a gene is called

allele

In pea plants, height is controlled by a single gene with tall being dominant to short. If two heterozygous plants are crossed, what proportion of the tall progeny will be homozygous dominant?

1/4

2/3

1/3

1/2

1/3

All offspring:

25% TT
50% Tt
25% tt

There are 3 tall offspring total.

Of those 3:

1 is TT

Mendel studied the inheritance of seed shape with alleles R and r along with seed color with alleles Y and y. He crossed true-breeding pea plants with genotypes RRYY and rryy to give an Fy generation with the genotype RrYy. If the Fy plants produced equal numbers of four types of gametes, RY, Ry, rY, and ry, this would indicate that the genes for seed color and shape

are closely linked on the same chromosome

are independently assorting

have recombined to form new combinations

are independently assorting

• are closely linked on the same chromosome
  Reason: Incorrect. Linked genes will result in a greater proportion of gametes with parental genotypes.

• are independently assorting
  Reason: Correct.

• have recombined to form new combinations
  Reason: If these genes were on the same chromosome and the allelic combinations were due to recombination, there would be fewer recombinant gametes and more gametes with the original parental combination.

Alleles of different genes are distributed into gametes independently of one another.

Imagine you're choosing:

Seed shape:

R or r

AND separately:

Seed color:

Y or y

You can get any combination:

R + Y = RY

R + y = Ry

r + Y = rY

r + y = ry

Heterozygous vs Heterogenous

-zygous → genetics/alleles 🧬
-geneous → types/things 🧩

The random arrangement of homologs along the metaphase plate in meiosis I is consistent with Mendel's law of

independent assortment

Mendel analyzed crosses involving two different characters simultaneously: seed shape and seed color. Two hypotheses can explain how the two different genes assort during gamete formation. According to the figure shown here, the genes for seed shape and color.

are on separate chromosomes

are linked on the same chromosome

are independently assorting

have recombined to form new combinations

are linked on the same chromosome

There are TWO possibilities

The question says there are two hypotheses for how these genes behave.

POSSIBILITY 1: Genes are on separate chromosomes

If the genes are on different chromosomes, they can assort independently.

An RrYy plant can make:

RY, Ry, rY, ry

So you'd expect 4 types of gametes.

POSSIBILITY 2: Genes are linked on the same chromosome

If the genes are physically located near each other on the same chromosome, they tend to travel together.

Because the original parents were:

RRYY × rryy

So the F₁'s arrangement is:

RY / ry

If the genes stay together, the F₁ mainly produces:

RY and ry

That's only 2 types of gametes.

The behavior of chromosomes during meiosis explains Mendel's law of segregation. Specifically, a gamete contains only one copy of each type of chromosome because of which of the following?

The homologs segregate during meiosis I and the sister chromatids separate during meiosis Il.

The sister chromatids segregate during meiosis I and then again during meiosis II.

The homologs segregate during meiosis I and then again during meiosis II.

The sister chromatids segregate during meiosis I and the homologs separate during meiosis II.

The homologs segregate during meiosis I and the sister chromatids separate during meiosis Il.

What is the genotype of II-4 based on the following pedigree of a recessive trait?

Homozygous recessive

Heterozygous

Homozygous dominant

Heterozygous

Reason: The female in II-4 is not expressing the trait, but her offspring are. Thus, she cannot be homozygous recessive, but heterozygous.

Mendel's law of independent assortment can be explained by the random alignment of ____ during ____ of meiosis I.

homologous chromosomes

metaphase 1

A cross is made between AaBbCcDD and AABbcDD individuals. Rather than making a very large Punnett square, which statistical operation could you use to solve this problem, and what would be the probability that the cross produces an offspring that is AAbbccDD?

Product rule, 1/64

Product rule, 1/16

Product rule, 1/4

Binomial expansion, 1/64

Binomial expansion, 1/16

Binomial expansion, 1/4

Product rule, 1/16

Gene	Cross	Need	Probability
A	Aa × AA	AA	1/2
B	Bb × Bb	bb	1/4
C	Cc × cc	cc	1/2
D	DD × DD	DD	1

Consider the following pedigree of a recessive trait. What is the genotype and phenotype of II-2?

Genotype: Homozygous dominant;

Phenotype: Expressing the trait

Genotype: Homozygous recessive;
Phenotype: Not expressing the trait

Genotype: Homozygous dominant or heterozygous;
Phenotype: Not expressing the trait

Genotype: Homozygous dominant or heterozygous;

Phenotype: Expressing the trait

Genotype: Homozygous dominant or homozygous recessive;

Phenotype: Expressing the trait

Genotype: Homozygous dominant or heterozygous;
Phenotype: Not expressing the trait

Two true-breeding stocks of corn are crossed. The first parent had purple, smooth grains and the second had yellow, shrunken grains. All the F, individuals were like the first parent. The Fy was allowed to self-hybridize, and the following Fz data were obtained:

Purple, shrunken grains 204

Yellow, shrunken grains 68

Purple, smooth grains 701

Yellow, smooth grains 243

You propose a hypothesis that this cross is an example of a typical Mendelian dihybrid cross in which the two genes assort independently. What is the chi-square value for this experiment?

3.08

5.22

3.53

4.77

4.11

4.77

The probability of producing a short plant from two heterozygous parents is . What is the likelihood that these same parent plants will produce 3 short plants?

¾ 75%

1/32 3.1%

1/8 12.5%

1/64 1.6%

¼ 25%

1/64 1.6%

¼ x ¼ x ¼ = 1/64