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Biochemistry > Mendelian Genetics and Inheritance > Flashcards

Mendelian Genetics and Inheritance Flashcards

1
Q

what is tooth agenesis?

A
  • failure of a tooth to form
  • the most common heritable disorder in humans
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2
Q

tooth agenesis affects ___% of the population worldwide, if ___ are excluded

A
  • 4-7%
  • 3rd molars
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3
Q

of the population affected by tooth agenesis, ___% are missing 3 or more teeth

A

1%

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4
Q

if 3rd molars are included in tooth agenesis stats, ___% of the population is considered to be affected by tooth agenesis

A

20%

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5
Q

mendelian genetics is a model of ___ first described by gregor mendel

A

inheritance

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6
Q

what is a phenotype?

A

a physical trait

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7
Q

mendel cross bred plants with various phenotypes and recorded the ratio of offspring across generations. this led him to formulate his ___

A

3 laws of inheritance

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8
Q

name the 3 laws of inheritance

A
  1. the law of segregation
  2. the law of independent assortment
  3. the law of dominance
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9
Q

what is the law of segregation?

A
  • factors for each trait segregate, such that each gamete carries only one factor for each trait
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10
Q

what is the law of independent assortment?

A

each factor that segregates does so independently

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11
Q

what is the law of dominance?

A

some factors are dominant and some are recessive. the dominant trait will always be expressed when present

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12
Q

what are mendel’s heritable factors referred to as?

A

alleles

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13
Q

what are alleles?

A
  • the different forms of a gene
  • for example, flower color
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14
Q

law of segregation

there are ___ copies of each allele, and further, they are ___

A
  • two
  • separated
  • consider meiosis: diploid (2n) cells become haploid (1n)
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15
Q

the law of segregation

one copy of a ___ comes from one parent, and the other copy comes from the second parent

A

gene (allele)

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16
Q

law of independent assortment

mendel concluded that not only did copies of a single allele separate, but that alleles for different traits separated ___ of one another

A
  • independently
  • for example: flower color and seed color both have an allele with 2 copies. both of these alleles will be distributed according to the law of segregation, but will do so independently of one another.
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17
Q

law of independent assortment

the number of ___ depends on the number of ___ we are considering

A
  • combinations
  • alleles
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18
Q

law of dominance

mendel observed that each trait has a ___ and ___ form

A

dominant and recessive

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19
Q

law of dominance

a ___ allele will always be expressed when present

A

dominant

20
Q

law of dominance

what must occur in order for a recessive allele to be expressed?

A

both copies of the allele must be recessive

in other words, the dominant allele must not be present

21
Q

describe the difference between homozygous and heterozygous

A
  • homozygous: organisms can be either homozygous dominant or homozygous recessive, and therefore will only pass along the allele they express
    • ex. AA or aa
  • heterozygous: organisms will always express the dominant allele, while carrying (and passing) the recessive allele
    • ex. Aa
22
Q

does dominance imply normality?

A

no; it is simply preferred expression

23
Q

dominance is not ___, but relative to an allele that is also present

A

inherent

24
Q

T or F:

dominant traits are always the most common in a population

A

false:

they can actually be rare

25
Q

what is a genotype?

A

alleles that are present

vs. phenotype, which are the traits that are expressed

26
Q

in mendel’s observations from his second generation crosses, he observed a phenotypic ratio of ___:___

A

3 dominant : 1 recessive

27
Q

in the first generation, assuming a cross between two “true breeding” or homozygous organisms, we will always get what? what laws of inheritance do we see here?

A
  • heterozygotes, expressing the dominant allele
  • 1st and 3rd laws
28
Q

once we start crossing the results of the F1 generation, are we dealing with true breeding parents?

A

no

29
Q

breeding of what generation yields mendel’s 3:1 phenotypic ratio?

A

breeding of the F1 generation, so the F2 generation shows the 3:1 phenotypic ratio

30
Q

what is the phenotypic composition of the F2 generation when parents of the F1 generation are true breeders? which laws of inheritance are seen?

A
  • 50% true breeding (homozygous) and 50% heterozygous organisms
  • 1st and 3rd laws
  • this will be the result regardless of the offspring chosen from the F1 generation
31
Q

the fact that recessive genes can be carried allows the ___ of certain genes, even if they aren’t favored when expressed.

A
  • preservation
  • it will eventually allow a recessive phenotype to resurface should environmental selection pressure change
32
Q

___ and ___ allows a species to resist extinction

A

genetic variability and selection

33
Q

any patterns of inheritance which do not strictly follow the three laws of inheritance are said to be ___

A

non-mendelian

34
Q

what are two examples of co-dominance?

A
  1. more than two possible alleles, even though each individual only carries two copies
  2. situations where more than one of these possible alleles are dominant, and can be expressed as a distinct co-dominant phenotype
35
Q

blood groups are an example of what?

A

co-dominance

*non-mendelian genetics

36
Q

what is incomplete dominance?

A

snapdragon example

  • if the alleles for white flowers (recessive) and red flowers (dominant) are both present, you end up with a weaker expression of red, resulting in pink flowers
  • there is no allele for pink flowers, but it is a possible phenotype when both red and white alleles are present
37
Q

what is mosaicism?

A
  • when different cells in the body have different genotypes, and thus express different phenotypes
  • calico cats are an exmaple
38
Q

sex-linked dominance

a __-linked trait would only be passed on to male offspring, and is relatively small so it contains ___ genes.

A
  • Y
  • fewer
39
Q

sex-linked dominance

for __-linked dominant traits, inheritance depends on the relative genotypes of the parents

A

X

40
Q

sex-linked dominance

a father with a dominant X trait will pass it to his ___ but not his ___. a mother would distribute ___% of all offspring depending on her genotype.

A
  • daughters
  • sons
  • 50-100%
41
Q

sex-linked dominance

which traits will predominate in males? which females will be affected?

A
  • X-linked recessive
  • females who are homozygous are affected
42
Q

sex-linked dominance

___ in females can result in limited expression of an X-linked recessive trait

A

X-inactivation

43
Q

what is extranuclear inheritance? what is an example?

A
  • factors passed form the cytoplasm
  • ex. mitochondrial DNA all comes from the ova
44
Q

___ is a recombination event where DNA sequence from one homologous chromosome can replace a sequence on its counterpart.

A

gene conversion

45
Q

gene conversion can interfere with ___

A

mendelian ratios

46
Q

describe infectious heredity

A

when integrated traits introduced by a virus are passed along the germ line; this is typically passed directly along from one parent

47
Q

T or F:

traits result as equal contributions from parent organisms

A

not always

Biochemistry (32 decks)

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