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Biology > Patterns of inheritance > Flashcards

Patterns of inheritance Flashcards

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AP® Biology flashcards Biology 101 flashcards
1
Q

What is an allele?

A

Different versions of a gene

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2
Q

What is a Genotype?

A

A combination of alleles.

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3
Q

What is a Phenotype?

A

The physical expression of a Genotype

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4
Q

What is a dominant allele?

A

Only need 1 allele for it be expressed in phenotype

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5
Q

What is a recessive allele?

A

Need two recessive alleles for for it to be expressed in phenotype

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6
Q

What does homozygous mean?

A

When the alleles are the same so either they are both recessive or both dominant

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7
Q

What does heterozygous mean?

A

When the alleles are different so one is recessive and one is dominant

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8
Q

What type of letter is used to denote a dominant allele?

A

A capital

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9
Q

What type of letter is used to denote a recessive allele?

A

A lowercase

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10
Q

What is a genetic cross?

A

A genetic cross can be drawn to show the probabilities of offspring inheriting different genotypes.

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11
Q

Why are genetic/offspring ratios often different from those expected?

A

> offspring ratios are a probability - they are not fixed and arise by chance
gametes may not be produced in equal numbers
fertilisation/fusion of gametes is random
small sample

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12
Q

What are the chromosomes’ for a girl?

A

XX

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13
Q

What are the chromosomes’ for a boy?

A

XY

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14
Q

What are Co-dominant alleles?

A

Both alleles are dominant and both are expressed in the phenotype, e.g. AB blood group.

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15
Q

What are the chromosomes for a male?

A

X Y

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16
Q

What are the chromosomes for a girl?

A

X X

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17
Q

Which chromosome does a male get from his father?

A

Y

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18
Q

What chromosome do females get from each parent?

A

X

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19
Q

What are genes located on a sex chromosome called?

A

Sex linked genes

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20
Q

Who can fathers pass sex-linked alleles too?

A

Only Daughters

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21
Q

Who can mothers pass sex linked alleles too?

A

Sons and Daughters

22
Q

What chromosome are most sex linked conditions passed via?

A

X

23
Q

What are some examples of sex linked conditions?

A

•colourblindness
• haemophilia
• duchennes muscular dystrophy (DMD)

24
Q

Why are observed offspring ratios are often not the same as expected ratios?

A

Fertilisation is random - fusion of gametes is random

25
Q

Why are males more likely to show a phenotype produced by a recessive allele carried on the X chromosome?

A

Females could be heterozygous/carriers
For a female both her chromosomes would have to carry the recessive allele.

26
Q

What does dominant epistasis mean?

A

Dominant 1st gene masks the expression of the 2nd one

27
Q

What is recessive epistasis?

A

If the 1st gene is recessive and isn’t expressed the second cant be.

28
Q

Define species

A

A group of organisms which can interbreed and produce fertile offspring

29
Q

Whats speciation?

A

Means the development of a new species and it can occur when populations are reproductively isolated in some form.

30
Q

What is allopatric speciation?

A

When there is a geographic barrier that separates the populations, like a river or mountain that keeps them from being able to interbreed and share the same gene pool.

31
Q

What is sympatric speciation?

A

The speciation happens in the same area, yet there’s something else isolating them such as prezygotic barriers or postzygotic barriers.

32
Q

What are examples of prezygotic (before zygote can be made) barriers?

A

> behavioural isolation - different behaviours that can isolate them such as birds having different songs/ different courtship which can prevent the males from attracting the females of other populations.

> temporal isolation - species could breed at different seasons, years, different times.

> habitat isolation - even assuming that organisms live in the same area doesn’t mean their habitats are exactly the same such as one prefers an aquatic environment and one prefers a terrestrial environment.

33
Q

What are examples of postzygotic (zygote is formed) barriers?

A

> offspring are unable to reproduce
offspring produced between 2 different species are very weak and do not survive long
interbred offspring are not able to develop in even very early embryonic stags because their is genetic incompatibility

34
Q

What is bottleneck?

A

Significant reduction in the size of a population due to environment events or human activities

35
Q

What is the Chi-Squared test used for?

A

To determine if there is a significant association between categorical variables.

36
Q

What is continuous variation?

A

Traits that can take on a range of values rather than distinct categories.

37
Q

Define dihybrid

A

An organisms that is heterozygous for two specific traits

38
Q

Whats directional selection?

A

Type of natural selection that occurs when individuals with a certain phenotype are favoured over others

39
Q

Whats discontinuous variation?

A

Traits that exhibit distinct categories

40
Q

What is epistasis?

A

Where the expression of one gene is affected by one or more other genes.

41
Q

What is the founder effect?

A

When a small group of individuals becomes isolated from a larger population.

42
Q

What is genetic drift?

A

Random changes in allele frequencies within a population overtime.

43
Q

What does the Hardy-Weinberg equation show?

A

Describes the genetic variation in a population at equilibrium. It shows the frequency of a particular allele is the proportion it represents of all the alleles of a gene. Frequency is always less than 1 so always a decimal.
p + q = 1
p^2 + 2pq + q^2 = 1

44
Q

Whats an isolating mechanism?

A

Prevents different species’ from interbreeding

45
Q

What is linkage?

A

Genes are located close together on the same chromosome to be inherited together during meiosis.

46
Q

Whats a monohybrid?

A

Organisms that are heterozygous for a single trait.

47
Q

Whats sex linkage?

A

The association of certain genes with the sex chromosomes - X or Y

48
Q

Whats stabilising selection?

A

Type of natural selection that favours the average, removing extremes.

49
Q

Whats variation?

A

Differences in traits among individuals within a population.

50
Q

In the Hardy-Weinberg equation what does the p and q stand for?

A

p = frequency of dominant allele
q = frequency of recessive allele

51
Q

In the Hardy-Weinberg equation what does the p^2 and q^2 stand for?

A

Genotype frequencies

52
Q

How do you use the results of a Chi-squared test?

A

You compare the calculated Chi-square value to a critical value from the Chi-squared distribution at a specific level of significance usually 0.05. If the calculated value is greater than the critical value, then the results are considered statistically significant, indicating that there is a relationships between the variables being studied.

Biology (12 decks)

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