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GED- Genes > Mendel’s Law > Flashcards

Mendel’s Law Flashcards

1
Q

At which stage of meiosis are homologous chromosomes separated?

A

Anaphase I

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2
Q

How many bivalents can be seen in humans at prophase I of meiosis if 2n = 46?

A

23 bivalents

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3
Q

Who is considered the founder of genetics?

A

Mendel

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4
Q

What is Mendel’s principle of Dominance?

A

One allele can mask the expression of another allele.

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5
Q

What is the phenotypic ratio in a monohybrid cross in the F2 generation?

A

3:1

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6
Q

What is the phenotypic ratio in a dihybrid cross in the F2 generation?

A

9:3:3:1

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7
Q

Fill in the blank: Mendel’s first law states that members of a gene pair ______ into gametes equally.

A

segregate

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8
Q

What does the term ‘pleiotropy’ refer to?

A

A gene influencing more than one trait.

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9
Q

What is an example of a recessive lethal allele?

A

Yellow allele in mice.

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10
Q

What is the main cause of Achondroplasia?

A

A dominant gain-of-function mutation in FGFR3.

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11
Q

True or False: Incomplete dominance results in a phenotype that is a blend of both alleles.

A

True

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12
Q

What is the definition of ‘penetrance’ in genetics?

A

The percentage of individuals with a given genotype who exhibit the expected phenotype.

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13
Q

What is ‘variable expressivity’?

A

The extent to which a genotype is expressed at the phenotypic level.

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14
Q

What is the significance of Alfred Knudson’s two hit hypothesis?

A

It explains familial cancer syndromes caused by tumor suppressor genes.

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15
Q

What are the three types of point mutations?

A
  • Silent (no effect)
  • Nonsense (changes code)
  • Missense - either conservative (subtle effect) or nonconserative (causes problem in protein)
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16
Q

What is the relationship between dominance and recessiveness?

A

Dominance/recessiveness is a relationship between two alleles, not a fixed property.

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17
Q

What does ‘loss of heterozygosity’ mean?

A

The loss of the healthy allele in a heterozygous individual due to mutation.

18
Q

Fill in the blank: The universal donor blood type is ______.

A

O

19
Q

What is the expected phenotypic ratio of a cross involving a yellow allele that is dominant for coat color?

A

2:1 due to recessive lethality.

20
Q

What does co-dominance mean in genetics?

A

Both alleles in a heterozygote are fully expressed.

21
Q

What is meant by ‘multiple alleles’?

A

More than two alleles exist for a gene within a population.

22
Q

Give an example of a genetic condition affected by pleiotropy.

A

Primary ciliary dyskinesia (PCD).

23
Q

What is the impact of gene modifiers on phenotypic expression?

A

They can affect the expression of a phenotype.

24
Q

What does Mendel’s First Law state?

A

Alleles of a single gene segregate randomly and equally into gametes

This law explains how each gamete inherits only one of the two alleles with equal probability.

25
Q

What is the key process during Metaphase I in meiosis?

A

Homologous pairs line up at the equator

This alignment is crucial for the proper segregation of chromosomes.

26
Q

What is Mendel’s Second Law?

A

Alleles from different genes segregate randomly into gametes

This law is based on the independent assortment of chromosomes.

27
Q

Which scientists contributed to the chromosome theory of inheritance?

A

Walter Sutton and Theodor Boveri

Their work in the early 1900s established parallels between Mendel’s laws and chromosome behavior.

28
Q

What did Thomas Hunt Morgan use to demonstrate that genes are located at specific regions of chromosomes?

A

Fruit fly

Morgan’s work earned him a Nobel Prize in 1933.

29
Q

What occurs during Meiosis II?

A

Segregation of sister chromatids

This process ensures that each gamete receives only one chromatid from each chromosome.

30
Q

In the context of Mendel’s laws, what is the significance of equal probability in gamete formation?

A

Each type of gamete is produced with equal probability

This is essential for the genetic variation seen in offspring.

31
Q

Fill in the blank: Mendel’s First Law derives from the segregation of _______ in Meiosis I.

A

homologous chromosomes

This segregation leads to the formation of equal numbers of different types of gametes.

32
Q

True or False: Mendel’s Second Law is a consequence of the random alignment of pairs of homologous chromosomes.

A

True

This alignment occurs during Metaphase I of meiosis.

33
Q

What is produced at equal frequency in the gametes according to Mendel’s Second Law?

A

Each possible combination of alleles

This reflects the independent assortment of alleles from different genes.

34
Q

What is the principle of independent assortment?

A

Only works if genes are on different chromosomes or very far apart

35
Q

What is Mendel’s theory of inheritance?

A
  • characters are distinct and hereditary determinants (genes) are particular in nature
  • each adult has 2 genes (from mother and father) for each character = alleles
  • members of the gene pair segregate equally into gametes (meiosis) so that the gamete is haploid
  • fusion of gametes at fertilisation restores diploidy
  • different genes assort independently in gametes
36
Q

What is the effect of a nonsense mutation?

A

Causes truncated form

Null allele = no activity from that protein

(Loss of function)

37
Q

What is the effect of a missense mutation?

A

Conservative - slight effect on function of enzyme, no effect on phenotype but may have slightly reduced activity = loss or gain of function

Nonconservative - causes loss or gain (always active) of function

38
Q

What are the general rules of mutations?

A
  • LOF alleles are mostly recessive
  • GOF alleles are mostly dominant
39
Q

What is incomplete dominance?

A

Heterozygote phenotype is intermediate between the 2 homozygote phenotypes

40
Q

What is co-dominance?

A

Heterozygote shows phenotype of both alleles

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