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Biology > Chapter 8: Inheritance, Genes, and Chromosomes > Flashcards

Chapter 8: Inheritance, Genes, and Chromosomes Flashcards

1
Q

What is crossing over?

A

Exchange between non-sister chromatids that produces recombination between DNA molecules

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2
Q

What is independent assortment?

A

Haploid sets of chromosomes inherited from parents, mixed by segregation of homologs during Meiosis

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3
Q

What is a chiasma?

A

The point of contact or physical link between two (non-sister) chromatids belonging to homologous chromosomes

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4
Q

What is produced as a result of crossing over?

A

Recombinant DNA/chromatids

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5
Q

What do haploid gametes represent?

A

parental chromosomes

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6
Q

How do you calculate the number of possible combinations of chromosomes in cells?

A

2^n where n is the number of homologous pairs

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7
Q

In what phase of meiosis does crossing over occur?

A

Prophase 1

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8
Q

In what phase of meiosis does independent assortment occur?

A

Anaphase 1

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9
Q

Does crossing over and independent assortment occur during Meiosis 1 or Meiosis 2?

A

Meosis 1

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10
Q

Mendel’s first law

A

Law of segregation: The two alleles of a gene separate and are transmitted individually and equally to gametes

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11
Q

Outcome of the law of segregation

A

50% gametes with allele 1 and 50% of gametes with allele 2

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12
Q

Pure-breeding lines

A

same phenotype occurs each time individuals are crossed within the line

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13
Q

Inference

A

the lines are homozygous containing the same allele on both homologous chromosomes

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14
Q

What is the P generation?

A

parental generation

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15
Q

What is are F generations?

A

Offspring, and their offspring, and so on

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16
Q

Homozygote

A

Has an identical genotype (ex. AA)

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17
Q

Heterozygote

A

has a varied genotype (ex. Aa)

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18
Q

What is a test cross?

A

Take a organism that has a genome you don’t know, and cross it with a homozygotes to find out what the mystery genome is

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19
Q

Locus

A

A particular site on a chromosome

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20
Q

What is a gene?

A

a sequence within a DNA molecule that resides at a locus; the function of the gene influences characteristics of an organism; its a protien

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21
Q

T/F different aleles segregate equally to gametes during meiosis according to the law of segregation

A

T; because genes are shared by homologous chromosomes

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22
Q

What mechanism is responsible for the law of segregation?

A

The transmission of chromosome pairs through meiosis

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23
Q

Mendel’s second law

A

The law of independent assortment; alleles of different genes assort independently during gamete formation

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24
Q

Outcome of independent assortment

A

25% of gametes with each combination of alleles at two loci

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25
Q

What is the probability for each phenotype in a dihybrid cross?

A

Both dominant 9/16
Half dominant 3/16
Other half is dominant 3/16
Both recessive 1/16

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26
Q

Alleles of genes on different chromosomes _______ during gamete formation

A

assort independently

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27
Q

Linkage

A

alleles of separate loci are transmitted together to offspring

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28
Q

What are parental types?

A

look like the parent (phenotype) but doesn’t necessarily have the same genotype

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29
Q

What does Mendel’s 2nd Law

A

recombinant types

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30
Q

Each chiasma involves ____ non-sister chromatids of the tetrad. What does it produce?

A

2
2 recombinant chromatids

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31
Q

What does one crossover produce?

A

two recombinant gametes and two parental gametes

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32
Q

How can you tell if there is linkage?

A

There is an excess of parentals over recomninants

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33
Q

How do you calculate recombinant frequency?

A

of recombinants / # of total offspring

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34
Q

Genes that are closer together are going to have _____ recombinants

A

fewer

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35
Q

What is the maximal recombinant frequency

A

0.5

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36
Q

When is there no linkage

A

They are either on the same chromosome or so far apart on two different chromosomes that there is always a crossover

37
Q

Is absolute linkage rare? Why or why not?

A

Rare; even alleles of different loci that are very close on the same chromosomes are sometimes recombined by crossing over

38
Q

What are the three key principles of genome-wide inheritance

A

segregation, independent assortment, recombination

39
Q

What forms a linkage group

A

All of the loci on a chromosome

40
Q

What is the distance between genes? What is it called?

A

Called a map unit or centimorgan (cM)
100 x recombinant frequency

41
Q

What is the genetic size of all autosomes

A

3,590 cM

42
Q

What is the genetic size of an X chromosome

A

195 cM

43
Q

If given distances, and trying to find the recombinant frequency

A

find the different of the distances and divide by 100

44
Q

When is recombinant frequency 0.5?

A

If recomb frequency = 0.5 or is greater than 0.5

45
Q

What are sex chromosomes? What are autosomes?

A

Sex chromosomes are the genes with primary control of sexual development and are present on the sex chromosomes
Autosomes are all other chromosomes

46
Q

Home many chromosomes are in the human karyotype

A

23 pairs (2n = 46)
22 pairs autosomes, a single pair of sex chromosomes

47
Q

Which gender is which genotype

A

Female: XX
Male: XY

48
Q

How many gametes produced by males determine the sex of a zygote

A

2

49
Q

What is the SRY gene?

A

sex-determining region on the Y; encodes a protein that initiates male development

50
Q

What do sex chromosome abnormalities result from?

A

nondisjunction in meiosis; pair of homologous chromosomes fail to separate in Meiosis 1 or a pair of sister chromatids fail to separate in Meiosis 2

51
Q

What is the genotype of Turner syndrome? Klinefelter syndrome?

A

Turner: X, only one sex chromosome
Klinefelter syndrome: XXY, affects males are results I sterility and overlong limbs

52
Q

Genes on sex chromosomes exhibit _____

A

sex-linked inhertiance

53
Q

Which carries more genes X or Y

A

X cares many, Y carries a few

54
Q

T/F males have two copies of genes of the X

A

False; males have only one copy of the genes of the X (hemizygous) and express the phenotype of that allele

55
Q

What are traits of X-linked recessive phenotypes

A

appear much more often in males than females; heterozygous females are carriers; phenotype can skip a generation if it passes from a male to his daughter and then grandson

56
Q

Drosophila melanogaster Karyotype

A

4 pairs of homologous chromosomes (2n = 8)
3 pairs of autosomes (2 large, 1 small)
single pair of sex chromosomes

57
Q

Drosophila in general

A

Female has XX
Male has XY
Males produce two types of gametes that determine the sex of the zygote

58
Q

In Drosophila, the number of X chromosomes establishes _________

A

alternative pathways of female (2X) or male (1X) development

59
Q

What do sex chromosomes contain?

A

the gene(s) that determine sex and exhibit unique patterns of inheritance

60
Q

Bees Sex Determination Mechanism

A

males are haploid, females are diploid

61
Q

Fruit Flies Sex Determination Mechanism

A

Fly is female if the ratio of X chromosomes to sets of autosomes is 1 or more

62
Q

Birds Sex Determination Mechanism

A

Males ZZ (homogametic), females WZ (heterogametic)

63
Q

Mammals Sex Determination Mechanism

A

Males XY (heterogametic)
Females XX (homogametic)

64
Q

What is the first clue of sex linkage

A

Reciprocal Crosses

65
Q

What is hemizygous expression?

A

When there is only one copy of genes, which is the phenotype

66
Q

What is complete dominance

A

The heterozygotes appear similar to one of the homozygotes; used to define dominant and recessive allele

67
Q

Why is one allele dominant over the other

A

It encodes a functional protein so that the one allele of the heterozygote is sufficient to produce the same phenotype as the two functional alleles

68
Q

When one gene is dominant over another, what does the recessive phenotype result from?

A

The absence of the functional protien that encodes the dominant gene

69
Q

With complete dominance, what is the ration of dominant offspring to recessive offspring?

A

Near 3

70
Q

Incomplete dominance

A

When heterozygotes have an intermediate phenotype that doesn’t take on the traits of the dominant or recessive phenotype

71
Q

With incomplete dominance, what does a monohybrid cross produce?

A

Produces a 1:2:1 ratio of phenotypes in F2, so that each genotype has a distinct phenotype (the intermediate phenotype)

72
Q

What are the alleles for coat color in rabbits? Which are dominant and recessive?

A

C (dominant) –> dark gray
c^chd –> chinchilla
c^h –> point restricted
c (recessive)–> albino

73
Q

What is co-dominance?

A

Phenotypes of both alleles appear in the heterozygote

74
Q

Physical characteristics reflect underlying _______ such as ________ within biochemical pathways

A

cellular functions
enzymatic activity

75
Q

Epistasis

A

The phenotype expression of one gene is influenced by the genotype of another gene

76
Q

What indicates epistasis

A

modified dihybrid phenotype ratio

77
Q

Probability of two independent events happing together

A

multiply

78
Q

Probability of an event occurring in two mutually exclusive ways

A

add

79
Q

For independently assorting loci, each locus can be treated as ___________ within the dihybrid cross

A

independent events

80
Q

Some traits of single gene disorders. What are the two types?

A

Rare, caused by a mutant allele of a single gene, results in a change in phenotype; recessive disorders and dominant disorders

81
Q

How many alleles need to be mutant in recessive disorders? What are a few examples?

A

Both alleles
Albinism, cystic fibrosis, PKU, sickle cell anemia, Tay-Sachs, muscular dystrophy

82
Q

How many alleles need to be mutant in dominant disorders? What are a few examples?

A

One allele
Huntington disease, achondroplasia

83
Q

General rule for dominant inheritance

A

affected individuals always have an affected parent

84
Q

General rule for recessive inheritance

A

Affected individuals can appear in families, even when both parents are unaffected

85
Q

Albinism

A

A = tyrosinase
a = mutant
aa does not make active tyrosinase & produces no melanin, resulting in albino phenotype

86
Q

Achondroplasia

A

A dominant form of dwarfism
d encodes growth factor receptor that functions as a negative regulator of long bone growth
D produces too much of the receptor and causes reduced growth of long bones

87
Q

What is the response of each genotype of achondroplasia

A

Dd = dwarfism
dd = normal stature
DD = lethal

88
Q

Describe Mendelian traits

A

single gene affecting discrete phenotypic differences. phenotypes vary continuously over a range due to the action of multiple different genes and the environment

89
Q

Examples of Mendelian traits

A

height, weight, skin pigment

Biology (12 decks)

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