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BIOL311 Principles of Genetics > Chapter 2 > Flashcards

Chapter 2 Flashcards

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1
Q

Mendel’s Experiments

A
  • Ensured phenotypes were all distinct and contrasting, and all controlled by single-gene inheritance
  • All plants were pure line (all offspring produced by matings within the members of that line were identical)
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2
Q

Mendel’s Model

A
  1. A gene is necessary for producing pea colour
  2. Each plant has a pair of this type of gene
  3. Gene comes in 2 forms (alleles)
  4. A plant can either be YY, Yy, or yy
  5. Phenotype of Yy is always yellow, Y is dominant over y
  6. Members of a gene pair separate equally into the cells that become sperm and eggs in meiosis: Law of Equal Segregation
  7. At fertilization, gametes fuse randomly, regardless of which alleles are present
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3
Q

What is a zygote?

A

Fertilized egg

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4
Q

What is a homozygote?

A

plant with a pair of identical alleles for a gene i.e AA or aa

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5
Q

What is a heterozygote?

A
  • plant with different alleles for a gene, Aa

- sometimes called monohybrid

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6
Q

What is homozygous dominant?

A

AA

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7
Q

What is heterozygous?

A

Aa

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8
Q

What is homozygous recessive?

A

aa

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9
Q

What is a genotype?

A

allele combinations underlying phenotypes

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10
Q

What is a monohybrid cross?

A

Aa x Aa

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11
Q

What are meiocytes?

A

Specialization cells that divide to produce sex cells i.e eggs and sperm

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12
Q

What are null alleles?

A

alleles that make proteins with zero function

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13
Q

What are leaky mutations?

A

Reduced level of enzyme function -> some wild type functions “leak” into mutant phenotype

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14
Q

What are silent mutations?

A

no functional impact, basically wild type

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15
Q

What does haplosufficient mean?

A

1 gene copy has enough function to produce a wild-type phenotype

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16
Q

What does haploinsufficient mean?

A

Null mutant allele will be dominant because single wild-type allele alone can’t provide enough product for normal function

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17
Q

What does new function mean?

A

When mutation results in a new function that is dominant in a heterozygote because the wild type cannot mask the new function

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18
Q

Null mutations are recessive in:

A

halposufficient genes, and dominant in halpoinsufficient

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19
Q

Depending on their action, mutant alleles can be:

A

dominant or recessive, question of dominance needs to be considered in analysis.

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20
Q

A dominant mutation in the heterozygous state will:

A

be expressed

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21
Q

A cross between heterozygous dominant and wild-type will result in:

A

1:1 phenotypic ratio

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22
Q

Principles of inheritance can be applied in 2 ways:

A
  1. Inferring genotypes from phenotypic ratios

2. Predicting phenotypic ratios from parents of known genotypes

23
Q

What is the homogametic sex?

A

Females, have a pair of sex chromosomes (XX)

24
Q

What is the heterogametic sex?

A

Males, have a non-identical pair of sex chromosomes (XY)

25
Q

Inheritance patterns of genes on sex chromosomes are different than:

A

those of autosomal genes

26
Q

What is a dioecious species?

A
  • A species that shows animal-like dimorphism, females bearing flowers have only ovaries and male bearing flowers have only anthers.
  • Some have non-identical sex chromosomes, some have no visibly different sex chromosomes
27
Q

Cytogeneticists divide X and Y chromosomes into:

A

differential and homologous regions

28
Q

Differential regions contain:

A

the most genes and have no counterparts on the other sex chromosome

29
Q

Genes in the differential region are:

A

hemizygous (half-zygous), most genes don’t take part in sexual function

30
Q

Y chromosome only contains:

A

A few dozen genes, most don’t have counterparts on the X chromosome

31
Q

What is sex linkage?

A
  • non-autosomes-sex chromosomes

- one sex does not have a pair of similar sex chromosomes, the other does

32
Q

What is X linkage?

A

When mutant alleles in the differential region of X chromosome show a single-gene inheritance pattern

33
Q

What is Y linkage?

A

When mutant alleles of few genes in differential region of Y chromosome have linkage

34
Q

A gene that is sex-linked can show:

A

Phenotypic ratios that are different in each sex

35
Q

X and Y chromosomes in human have 2 short:

A

homologous regions, one on each end

36
Q

What are pseudoautosomal regions 1 and 2?

A

Homologous regions that are autosomal-like, one or both of these regions pairs with the other sex chromosome during meiosis and undergoes crossing over

37
Q

Pseudoautosomal regions 1 and 2 allow:

A

X and Y chromosomes to act as a pair and separate into equal numbers of sperm

38
Q

Males only need to inherit a single:

A

X-linked recessive allele to express it, whereas females need 2

39
Q

How is sex-linked inheritance recognized?

A

By different phenotypic ratios in the 2 sexes of progeny and different ratios in reciprocal crosses

40
Q

What are autosomal recessive disorders?

A

When the affected phenotype is inherited as a recessive allele

41
Q

What are the patterns for autosomal recessive disorders?

A
  1. Disorder appears in progeny of unaffected parents

2. Affected progeny includes males and females

42
Q

What is the appearance of the pedigree for autosomal recessive disorders?

A
  • Look bare with a few black symbols

- Affected siblings with ppl in earlier and later generations not affected

43
Q

What are autosomal dominant disorders?

A

When the normal allele is recessive and the defective allele is dominant

44
Q

What is the pattern for autosomal dominant disorders?

A

Phenotype appears in every generation of the pedigree, affected mothers and fathers pass onto sons and daughters

45
Q

Why is the pattern for autosomal dominant disorders like that?

A

Appears in every generation because the abnormal allele carried by a person must have come from a parent in the preceding generation

46
Q

What are polymorphisms?

A

The coexistence of 2 or more reasonably common phenotypes of a biological property

47
Q

Morphs are often inherited as:

A

alleles of a single autosomal gene

48
Q

What is the X-linked recessive disorder pattern?

A
  1. More males than females show rare phenotype
  2. None of the offspring of an affected male show the phenotype, but daughters are “carriers” -> next gen = 1/2 of males are affected
  3. None of the sons of affected fathers show phenotype and do not pass it on
49
Q

What is the X-linked dominant disorder pattern?

A
  1. Affected males pass on condition to all females, but no sons
  2. Affected heterozygous females mating with unaffected male results in condition to 1/2 males and females
50
Q

What is Y-linked inheritance?

A
  • Only males inherit, from fathers passing it on
  • Maleness is linked to the Y chromosome
  • Inheritance patterns with an unequal representation of phenotypes in males and females can locate the genes connected to one of the sex chromosomes
51
Q

What is a test cross?

A
  • Cross used to determine the genotype of an individual that is expressing a dominant phenotype
  • Crossed with tester which is homozygous recessive
52
Q

Meiosis 1

A

Prophase 1: chromosomes condense
Metaphase 1: align on midline
Anaphase 1: homologous dyads pulled apart
Telophase 1: dyads arrive at pole and nucleus forms

53
Q

Meiosis 2

A

Prophase 2: chromosomes condense
Metaphase 2: aligns on midline
Anaphase 2: sister chromatids pulled apart
Telophase 2: nuclei re-form, each chromatid now considered chromosome

BIOL311 Principles of Genetics (19 decks)

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