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BIOL311 Principles of Genetics > Chapter 2 > Flashcards

Chapter 2 Flashcards

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
Inheritance patterns of genes on sex chromosomes are different than:
those of autosomal genes
26
What is a dioecious species?
- 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
Cytogeneticists divide X and Y chromosomes into:
differential and homologous regions
28
Differential regions contain:
the most genes and have no counterparts on the other sex chromosome
29
Genes in the differential region are:
hemizygous (half-zygous), most genes don't take part in sexual function
30
Y chromosome only contains:
A few dozen genes, most don't have counterparts on the X chromosome
31
What is sex linkage?
- non-autosomes-sex chromosomes | - one sex does not have a pair of similar sex chromosomes, the other does
32
What is X linkage?
When mutant alleles in the differential region of X chromosome show a single-gene inheritance pattern
33
What is Y linkage?
When mutant alleles of few genes in differential region of Y chromosome have linkage
34
A gene that is sex-linked can show:
Phenotypic ratios that are different in each sex
35
X and Y chromosomes in human have 2 short:
homologous regions, one on each end
36
What are pseudoautosomal regions 1 and 2?
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
Pseudoautosomal regions 1 and 2 allow:
X and Y chromosomes to act as a pair and separate into equal numbers of sperm
38
Males only need to inherit a single:
X-linked recessive allele to express it, whereas females need 2
39
How is sex-linked inheritance recognized?
By different phenotypic ratios in the 2 sexes of progeny and different ratios in reciprocal crosses
40
What are autosomal recessive disorders?
When the affected phenotype is inherited as a recessive allele
41
What are the patterns for autosomal recessive disorders?
1. Disorder appears in progeny of unaffected parents | 2. Affected progeny includes males and females
42
What is the appearance of the pedigree for autosomal recessive disorders?
- Look bare with a few black symbols | - Affected siblings with ppl in earlier and later generations not affected
43
What are autosomal dominant disorders?
When the normal allele is recessive and the defective allele is dominant
44
What is the pattern for autosomal dominant disorders?
Phenotype appears in every generation of the pedigree, affected mothers and fathers pass onto sons and daughters
45
Why is the pattern for autosomal dominant disorders like that?
Appears in every generation because the abnormal allele carried by a person must have come from a parent in the preceding generation
46
What are polymorphisms?
The coexistence of 2 or more reasonably common phenotypes of a biological property
47
Morphs are often inherited as:
alleles of a single autosomal gene
48
What is the X-linked recessive disorder pattern?
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
What is the X-linked dominant disorder pattern?
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
What is Y-linked inheritance?
- 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
What is a test cross?
- Cross used to determine the genotype of an individual that is expressing a dominant phenotype - Crossed with tester which is homozygous recessive
52
Meiosis 1
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
Meiosis 2
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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