Genetics - Week 3 Flashcards

1
Q

Are genes that are physically linked and close together likely to undergo recombination?

A

unlikely to undergo recombination because there are few opportunities to cross over

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2
Q

Are genes that are physically linked and far apart likely to undergo recombination?

A

more likely to undergo recombination because there are more opportunities to cross over

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3
Q

What are methods of fertilization?

A
  • crossing over

- independent assortment

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4
Q

What is self-fertilization?

A

combination of one’s own gametes to produce offspring by crossing over or independent assortment

  • no resulting offspring will be genetically identical to the parent
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5
Q

Why is self-fertilization not asexual reproduction?

A

gametes with half the ploidy level of the parental cell are produced

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6
Q

What is asexual reproduction?

A

offspring arise from a single parent (ie. not via fusion of gametes)

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7
Q

What are the pros of sexual reproduction?

A

more genetic variation, easier to adapt to environment

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8
Q

What are the cons of sexual reproduction?

A
  • have to actually find a mate
  • requires more energy and time
  • takes longer to produce offspring
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9
Q

What are the pros of asexual reproduction?

A

faster to produce offspring

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10
Q

What are the cons of asexual reproduction?

A

less genetically variable offspring

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11
Q

What is a genotype?

A

genetic make-up (or set of genes, combination of alleles) of an organism/individual

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12
Q

What is a phenotype?

A

any observable characteristics (traits) of an organism/individual as a result of its genotype and interaction with the environment

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13
Q

What are homozygotes?

A

(in diploid organisms) carry two copies of same allele for a particular gene

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14
Q

What are heterozygotes?

A

(in diploid organisms) carry different alleles

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15
Q

What is a test cross?

A

crossing of an individual with an unknown genotype with an individual with a homozygous recessive genotype

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16
Q

What are true breeding organisms (purebreds)?

A

homozygotes

17
Q

What are non-true breeding organisms?

A

heterozygotes

18
Q

What is incomplete dominance?

A

traits blend together

19
Q

What is co-dominance?

A

both traits appear

20
Q

What is a wild type?

A

refers to the most common form of the allele or phenotype, or the original allele/phenotype that was observed in

21
Q

What is a mutant?

A

refers to the less common and/or newer version of a gene/trait, that has arisen through mutation

22
Q

Describe the chromosomes in humans.

A

humans have 46 chromosomes in each diploid cell:

  • 44 autosomes (22 pairs)
  • 2 sex chromosomes (X and Y)
  • X (female) is bigger than Y (male)
23
Q

What are physically linked genes?

A

genes are on the same chromosome

24
Q

What are sex linked genes?

A

genes are on one of the sex chromosomes (either X-linked or Y-linked)

25
Q

What are X-linked genes?

A

X chromosomes in a female act like homologous autosomes (homozygous/heterozygous)

  • males only have one X chromosome (neither homozygous nor heterozygotes)
26
Q

What is a carrier?

A

heterozygotes which have a copy of the allele responsible for the gene of interest

27
Q

What are the 4 modes of inheritance?

A
  • autosomal dominant
  • autosomal recessive
  • X-linked dominant
  • X-linked recessive
28
Q

What may indicate sex-linkage of a trait?

A

if you see that the distribution of a trait varies between the male & female parents/offspring

29
Q

What are Punnett Squares used for?

A

to determine what the possible phenotypes and genotypes from fusing of gametes (crosses)

30
Q

How do you approach cross questions?

A
  • clearly state the symbols for each allele
  • look at the offspring data (F1 & F2) for hints regarding modes of inheritance (ie. are there differences between the sexes?)
  • provide a prediction for your hypothesis using Punnett Squares (or comparable methods using frequencies)
  • provide evidence to support your prediction using the frequencies (actual numbers) provided for the resulting F1 or F2 progeny that is provided
31
Q

How do you solve pedigree questions?

A

have a hypothesis, then, usually:

  • if a trait skips no generations: DOMINANT
  • unequal sex ratio: SEX-LINKED (on X chromosome)
  • if more males than females affected: X-LINKED RECESSIVE
  • if more females than males affected: X-LINKED DOMINANT
  • if the trait is not seen in parents, but is seen in their children (at least one): RECESSIVE
  • if a certain cross is not possible (due to genotypes): eliminates a mode of inheritance