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Biology > Patterns of inheritance > Flashcards

Patterns of inheritance Flashcards

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1
Q

What is continuous variation

A

Individuals in a population vary within a range

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2
Q

What is discontinuous variation

A

When there are two or more distinct categories

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3
Q

Define allele

A

Different versions of genes

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4
Q

How does meiosis make gametes with a unique assortment of alleles

A

Through crossing over and independent assortment of chromosomes

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5
Q

What is variation in phenotype

A

Phenotypic variation

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6
Q

What is polygenic characteristics and what type of variation are they normally

A

A characteristic influenced by two or more genes typically continuous variation

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7
Q

What is monogenic characteristics and what type of variation are they normally

A

Characteristics controlled by only one gene typically monogenic

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8
Q

Define gene

A

A sequence of bases on a DNA molecule that codes for a protein resulting in a characteristic

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9
Q

Define genotype

A

The alleles and organism has e.g BB

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10
Q

Define phenotype

A

The characteristics the alleles produce e.g brown eyes

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11
Q

Define dominant

A

An allele whose characteristic only appears in the phenotype even when there is only one copy shown by a capital letter

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12
Q

Define recessive

A

An allele whose characteristic only appears on the phenotype if two copies are present shown by lower case letters

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13
Q

Define codominant and an example

A

Alleles that are both expressed in the phenotype - neither one is recessive. Such as sickle cell anaemia

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14
Q

Define locus

A

The fixed position of a gene on a chromosome. Alleles of a gene are found at the same locus on each chromosome in a pair

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15
Q

Define homozygote

A

An organism that carries two copies of the same allele

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16
Q

Define heterozygote

A

An organism that carries two different alleles

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17
Q

Define carrier

A

A person carrying an allele which is not expressed in the phenotype but that can be passed on to offspring

18
Q

What is monogenic inheritance

A

Inheritance of a characteristic controlled by a single gene

19
Q

What does monogenic crosses show

A

The likelihood of different alleles of that gene being inherited by offspring of particular parents

20
Q

How to draw out a monogenic cross diagram steps

A

1) Parents genotypes
2) Gametes alleles
3) Possible genotypes of F1 offspring
4) Gametes alleles
5) Possible genotypes of F2 offspring
6) Phenotypes
7) Ratio in F2 offspring

21
Q

What is dihybrid inheritance

A

The inheritance of two characteristics which are controlled by different genes

22
Q

Expected phenotypic ratio of monogenic cross for F2 generation

A

3:1

23
Q

Expected dihybrid ratio of monogenic cross for F2 generation

A

9:3:3:1

24
Q

Expected phenotypic ratio of codominant cross for F2 generation

A

1:2:1

25
Q

Why wont the expected ratios from different types of genetic crosses occur

A

Sex linkage, autosomal linkage or epistasis

26
Q

What is a sex linked characteristic

A

When the allele that codes for the characteristic is located on a sex chromosome (X/Y)

27
Q

Why are males more likely to show recessive phenotypes that are sex linked than females

A

They only have one X chromosome and only one allele for sex-linked genes. As they only have one copy they express the characteristic of this allele even if it is recessive. Such as colour blindness

28
Q

What is an autosome

A

Any chromosome that is not a sex chromosome

29
Q

What are autosomal genes

A

Genes located on autosomes

30
Q

Genes on the same autosome are… and why

A

Linked - they will stay together during independent assortment of chromosomes in meiosis I and their alleles will be passed on to the offspring together unless crossing over splits them up before.

31
Q

What does the closer the genes on an autosome mean

A

They are more closely linked as crossing over is less likely to split them up

32
Q

Why won’t you see the expected phenotypic ratio of a cross that are autosomally linked

A

The two autosomally linked alleles are inherited together so there is a higher proportion of the offspring that will have their parents genotype and phenotype.

33
Q

What is epistasis

A

When the allele of one gene masks the expression of the alleles of other genes such as hair colour and baldness

34
Q

A dihybrid cross produces the phenotypic ratio of 9:3:4 in the F2 generation. What does this indicate about the genes involved

A

It involves a recessive epistatic allele

35
Q

A dihybrid cross produces the phenotypic ratio of 12:3:1 in the F2 generation. What does this indicate about the genes involved

A

Crossing a homozygous recessive with a homozygoua dominant

36
Q

What can the chi squared test be used for

A

To see if the results of an experiment support a theory

37
Q

What is a null hypothesis

A

There is no significant difference between the observed and expected results - results are due to chance

38
Q

How to work out the Chi-Squared Value

A

1) Work out the expected value for each phenotype
2) Record the actual number of offspring recorded
3) Subtract the expected result from the observed result
4) Square this number and divide by the expected result
5) Add all the numbers together to get the sum

X^2 = (O-E)^2 / E

39
Q

What is the critical value

A

The value of X^2 that corresponds to a 0.05 (5%) level of probability that the difference between the observed and expected results is due to chance

40
Q

When can the null hypothesis be rejected

A

If the X^2 value is larger or equal to the critical value then there is a significant difference

41
Q

When can the null hypothesis be accepted

A

If the X^2 value is smaller than the critical value and then there is no significant difference

42
Q

What are degrees of freedom

A

The number of phenotypes/classes

Biology (20 decks)

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