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Genetics Lecture > Exam II > Flashcards

Exam II Flashcards

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1
Q

What is a cross?

A

A mating that produces offspring.
Usually done multiple times.

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2
Q

What is a single-factor cross?

A

A cross involving one character controlled by one gene.

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3
Q

What is the parental (P) generation?

A

The first two individuals used for crossing. One individual will be homozygous dominant and the other will be homozygous recessive.

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4
Q

What is the first filial (F1) generation?

A

The offspring of the P generation. All offspring will be heterozygous.

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5
Q

What is the second filial (F2) generation?

A

The offspring of the F1 generation.

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6
Q

What is the difference between an autosome and a sex chromosome?

A

An autosome does not determine the genetic sex of an individual.
Sex chromosomes determine the genetic sex.

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7
Q

What are autosomal traits?

A

Traits produced by genes on autosomes.

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8
Q

What is Mendel’s Law of Segregation?

A

Basically “one allele of each autosomal gene is inherited from each parent.”

A parent has two alleles for each autosomal gene, which are separated from meiosis.
Each gamete has one of those alleles; offspring receive only one from each parent.

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9
Q

What is true-breeding?

A

A term meaning that an individual has a homozygous genotype.

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10
Q

How do you write out a potential cross?

A

__ __ x __ __
Punnett square.
yeah?

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11
Q

For incomplete dominance, what is a test-cross and what is it used for?

A

A cross between an individual with the dominant phenotype and one with the recessive phenotype. Test-crosses are used to distinguish the two genotypes

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12
Q

When is the 2:1 phenotypic ratio observed and why?

A

A 2:1 phenotypic ratio is observed whenever there is a lethal allele present. Typically, individuals that are homozygous for the lethal allele will not be alive, not contributing to the observations.

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13
Q

What is a sex-linked trait?

A

Traits produced by genes on sex chromosomes.

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14
Q

Why is the inheritance of sex-linked traits different from that of autosomal traits?

A

The two sexes, male and female, have different combinations of sex chromosomes.

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15
Q

Describe how males and females differ in the sex chromosome combinations.

A

Males: XY
Females: XX

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16
Q

Why aren’t the X and Y chromosomes considered a homologous pair?

A

The X and Y chromosomes are not considered homologous pairs because they have different sets of genes.

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17
Q

What are pseudoautosomal genes?

A

Genes found on BOTH X and Y genes.

18
Q

What are holandric genes?

A

Genes found only on the Y chromosome.

19
Q

What are X-linked genes?

A

Genes found only on the X chromosome.

20
Q

Genes in which category can be found on the X chromosome?

A

Pseudoautosomal and x-linked genes.

21
Q

Genes in which category can be found on the Y chromosome?

A

Pseudoautosomal and holandric genes.

22
Q

Which category contains the most genes?

A

Pseudoautosomal genes contain the most genes.

23
Q

Define the term hemizygous.

A

A genotype that consists of only one allele.

24
Q

What do the products of holandric genes do?

A

The product of holandric genes produces the trait of “maleness.”
Most important holandric gene: Sex-determining Region Y (SRY) gene.

25
Q

When does sexual differentiation of the human gonads begin?

A

Sexual differentiation begins at 7 weeks.

26
Q

Describe male sex determination during human embryonic development.

A

After 7 weeks of embryonic development, if the embryo is male, SRY will begin producing TDF.

27
Q

Explain the role of the SRY gene and its product TDF during male sex determination.

A

SRY produces Testis-Determining Factor (TDF).
TDF activates genes involved in testis formation and represses the ones for ovary production.

28
Q

What is XY-sex reversal, and how is it produced?

A

XY-sex reversal is when an individual presents a female phenotype but is genotypically male.
Occurs at birth.
It is caused by null alleles of the SRY gene.

29
Q

Which sex is more likely to inherit X-linked hypophosphatemia? Why?

A

Females are more likely to inherit X-linked hypophosphatemia. This is because the mutant, disease causing-allele is dominant (XH) and only found in X chromosomes.

30
Q

Which sex is more likely to inherit the red-green colorblindness trait? Why?

A

Males are more likely to inherit colorblindness. This is because the mutant allele is recessive and found only on the X chromosome. Females would have to be homozygous recessive to be colorblind while males simply need one recessive X allele.

31
Q

What is a two-factor cross?

A

Any cross involving two genes.
AKA dihybrid cross.

32
Q

Two-factor crosses and selective breeding?

A

Humans select two desirable traits for certain organisms.
“One character” is composed of multiple characters.
Think coat colors in cats (5 genes, each affecting different aspects of coat colors).

33
Q

Explain the difference between linked and unlinked genes.

A

Linked: genes on the same chromosome.
Unlinked: genes that are on different chromosomes.

34
Q

What are the shape and colors of the seeds in the common garden pea?

A

Color: Yellow (G), green (g)
Shape: Round (R), wrinkled (r)

35
Q

What is gene interaction?

A

Two genes working together to produce a single character.

36
Q

What are the four comb shapes in chickens?

A

Walnut
Rose
Pea
Single

37
Q

What two genes affect the comb shape in chickens?

A

Rose gene
Pea gene

38
Q

What is the dominant and recessive allele for the comb shape in chickens?

A

Rose gene = Dom: R; Rec: r
Pea gene = Dom: P; Rec: p

39
Q

Genotypes for walnut combs in chickens.

A

At least ONE dominant allele for both rose and pea genes.
RRPP, RrPp, RrPP, RRPp

40
Q

Genotypes for rose combs in chickens.

A

At least ONE dominant allele for rose gene and homozygous recessive for pea gene.
Rrpp, RRpp

41
Q

Genotypes for pea combs in chickens.

A

At least ONE dominant allele for pea gene and homozygous recessive for rose gene.
rrPP, rrPp

42
Q

Genotypes for single combs in chickens.

A

Homozygous recessive.
rrpp

Genetics Lecture (17 decks)

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