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Genetics > Mendellian Genetics > Flashcards

Mendellian Genetics Flashcards

1
Q

What were Mendel’s first 3 postulates?

A

1) unit factors are PAIRS
2) dominant/ recessive characteristics (called discontinuous variation)
3) separate INDEPENDENTLY

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2
Q

What is the basic unit of heredity?

A

Particulate unit factor

later called a GENE

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3
Q

What is an alternate form of a gene?

A

Allele

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4
Q

What is Mendel’s 4th postulate? And what does it lead to?

A

Independent assortment - leads to genetic variation

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5
Q

Why did Mendel choose peas for his experiment in the 1860’s?

A
  • easy to grow
  • true breeding
  • you can control their mating (because you transfer pollen from a stamen to a pistol )
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6
Q

How did Mendel determine that the peas genes were NOT sex linked?

A

RECIPROCAL CROSS

Regardless of which breed he took the pollen from, the results were the same.

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7
Q

Mendel had an odd finding in which generation of his experiment with dihybrid crosses? What was the odd finding?

A

In the F2 generation he found a genotypic ratio of 9:3:3:1

P1: 100% purebred
P2: 100% heterozygous for both traits
P3: 9:3:3:1 ratio

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8
Q

When do you use the product law?

A

When 2 events are happening simultaneously but independent

Ex: ratio of color x ratio of shape

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9
Q

What are passed from generation to generation unchanged?

A

Particulate unit factors (aka “genes”)

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10
Q

Which generation undergoes “selfing”?

A

The F1 undergoes selfing (mating with eachother) to yield an F2 generation

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11
Q

What is the principle of uniformity?

A

The appearance of heterozygotes are uniform phenotypically because of the dominance/recessive characteristics.

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12
Q

What is the chromosomal theory of inheritance (Sutton & Boveri, 1900’s)

A

Simply that genetic material is found in chromosomes

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13
Q

5 characteristics of being a homologous pair?

A

1) same size
2) identical centromere location (except x & y)
3) form pairs and synapse during meiosis
4) identical linear order of gene loci
5) 1 from mom & 1 from dad

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14
Q

Who suggested that variation was a blend of parent phenotypes and what was that called?

A

Continuous variation, suggested by Darwin & Wallace

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15
Q

Where are alternative forms of a gene found?

A

Homologous chromosomes

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16
Q

(SOLVING FOR # OF DIFFERENT TYPES OF GAMETES)

*What is the formula used to solve the scenario below:

On the basis of segregation and independent assortment, how many different types of gametes can be formed from an organism that has a diploid number of 12.

A

of copies (for diploid that’s 2) raised to the nth power.

Where n = the haploid number of chromosomes.

(In this scenario n=6. So 2^6 is 64.)

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17
Q

What is the term for an intermediate phenotype where neither allele is dominant

A

Incomplete or partial dominance

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18
Q

Example of an incomplete (partial) dominance

A

Red x White yields pink color

Phenotype ratio is the same but the genotypes have a blended intermediate

19
Q

What is an example of a human disorder with incomplete dominance?

A

Tay sachs disease

Homozygous recessives= fatal lipid storage disorder where hexosaminidase A is absent and can’t metabolize lipids. (Less than 50% threshold)

Normal heterozygotes: get 1/2 the enzyme activity but enough to live

20
Q

What is threshold affect?

A

Certainty level of the gene product attained. (Ex: tay Sachs disease has <50% threshold level)

21
Q

What is codominance?

A

When 2 alleles are expressed unblended. (Example: brown x white yields white with brown spots.)

22
Q

What is blood type an example of?

A

Codominance

IA and IB are codominant to eachother yielding AB blood type

23
Q

What are possible genotypes to yield type A blood

A

IA IA

and

IA i

24
Q

What are all the possible genotypes yielding an AB blood type

A

Only IA and IB

25
Q

What are all possible genotypes yielding type O blood

A

Only ii

26
Q

Explain Bombay phenotype

A

Female is functionally type O blood type even though she doesn’t have ii blood type.

She is homozygous for FUT1 (fucosyl transferase) so she can’t produce H substance and she can’t make A or B antigens

27
Q

Describe a recessive lethal allele

A

One wild type (normal) allele is enough to survive.

(Therefore, homozygous recessive will not survive.)

A lethal allele is a result of a mutation in “essential genes”

28
Q

What is an essential gene?

A

Required to survive

29
Q

What are results possible from dominant lethal alleles

A

One allele results in death

ie: Huntington’s

30
Q

What is epistasis? What is an example?

A

When a gene masks the phenotype of another gene

Ex: hereditary deafness and Bombay phenotype

31
Q

What predicts the number of genes determining a trait

A

Complementation analysis

32
Q

What is the complementation group?

A

When all mutations are present on the same gene in a complementation analysis

33
Q

What is it called when a single gene has multiple phenotypic effects?

A

Pleiotropy

34
Q

What are 2 examples of pleiotropy in human disorders

A

Marian syndrome

and

Porphyria variegata

35
Q

Describe pleiotropy

A

The expression of 1 gene has MULTIPLE phenotypic effects

36
Q

Porphyria variegata is an autosomal disorder that has multiple phenotypic effects

such as abdominal pain, muscular weakness, fever, racing pulse, insomnia, vision issues.

What builds up in the body when this disorder is present?

A

Polyphyrins buildup in the body to toxic levels

37
Q

What is the difference between sex limited and sex influenced inheritance?

A

Sex limited is limited to one sex only.

Whereas sex influenced is not limited to one sex. The sex of the individual influences the phenotypic expression - (aka sex influences phenotype).
Example: with male pattern baldness, the results are less pronounced in females.

38
Q

What is penetrance?

A

The percentage that a mutant phenotype is expressed in a population

39
Q

What is expressivity?

A

RANGE of the expression of the mutant phenotype

40
Q

What is position effect?

A

When the physical location of the gene influences its expression.

(When the chromosome is rearranged the phenotype looks different!)

41
Q

What is the temperature effect?

A

When the temp of the climate influences the gene.

Ex: Darker fur on cooler areas (tail, feet, ears)

42
Q

Examples of organisms that undergo Temperature sensitive mutations

A

Viruses, bacteria, fungi and DROSPHILIA

43
Q

4 examples of delayed onset disorders

A

Tay Sachs, lesch-nyhan, muscular dystrophy (DMD), Huntington’s

44
Q

What is genetic anticipation

A

Early onset but it gets more severe in each succeeding generation

Genetics (7 decks)

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