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Biology > Genetics > Flashcards

Genetics Flashcards

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AP® Biology flashcards Biology 101 flashcards
1
Q

What is a gene

A

a sequence of bases on a DNA molecule that codes for a protein (polypeptide) which results in a characteristic

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2
Q

What is an allele

A

Different versions of the same gene

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3
Q

How many alleles doe humans typically carry per gene

A

2, one from each parent

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4
Q

Why is the order of bases in each allele slightly different

A

because each allele codes for different versions of the same characteristic

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5
Q

Humans are

A

Diploid organisms

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6
Q

What does a diploid organism mean

A

we have two copies of each chromosome, one from each parent

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7
Q

What is the locus

A

The position of the allele on a gene

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8
Q

What is the genotype of an organism

A

Its genetic constitution/ the different alleles an organism has

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9
Q

What is the phenotype

A

the expression of genetic constitution and it’s interaction with the environment

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10
Q

What is a dominant allele

A

An allele that is always expressed in the phenotype

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11
Q

What are recessive alleles

A

They’re only expressed if two copies are present

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12
Q

What are codominant alleles

A

When both alleles are expressed in the phenotype because neither one is recessive

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13
Q

What does homozygous mean

A

When an organism carries two copies of the same allele

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14
Q

What does heterozygous mean

A

When an organism carries two different alleles for a gene

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15
Q

What are gametes

A

sex cells

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16
Q

How many alleles per gene do gametes contain

A

only one allele

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17
Q

What are haploid cells

A

A cell that contains a single set of chromosomes

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18
Q

What are diploid cells

A

A cell that contains two complete sets of chromosomes

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19
Q

What is monohybrid inheritance

A

The inheritance of a characteristic controlled by a single gene

20
Q

What is the phenotypic ratio

A

The ratio of different phenotypes in the offspring

21
Q

What is the usual ratio between two heterozygous parents

A

3:1, dominant : recessive

22
Q

One example of codominance

A

sickle-cell anaemia

23
Q

What is the expected ratio with two heterozygous parents involving codominant alleles

A

1:2:1

24
Q

What is dihybrid inheritance

A

The inheritance of two characteristics which are controlled by different genes. Each of the two genes will have different alleles

25
Q

What is the expected ratio with a dihybrid cross with two heterozygous parents

A

9:3:3:1

26
Q

What does it mean if some characteristics are sex linked

A

The alleles that code for them are located on a sex-chromosome

27
Q

What is the difference between X and Y chromosomes

A

Y is much smaller and carries fewer genes

28
Q

Why do men often only have one allele for sex-linked genes

A

As males only have one X chromosomes

29
Q

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

A

As they only have one copy they express the characteristic of this allele even if it’s recessive

30
Q

What are X-linked disorders

A

When faulty alleles for genetic disorders are carried on the X-chromosome

31
Q

What are X-linked genes

A

Genes on the sex chromosomes which are carried on the X-chromosome

32
Q

What does autosome stand for

A

Any chromosome that isn’t a sex chromosome

33
Q

What are autosomal genes

A

The genes located on the autosome

34
Q

Why are genes on the autosome said to be linked

A

Because they’ll stay together during the independent segregation of chromosomes in meiosis I and their alleles will pass on to the offspring together

35
Q

What prevents autosomal linkage

A

crossing over

36
Q

The closer together two genes are on the autosome the more closely they are said to be

A

linked because crossing over is less likely to occur

37
Q

What is epistasis

A

when two genes on different chromosomes affect the same feature. They interact to form the phenotype. One gene masks (blocks) the expression of the alleles of other genes.

38
Q

If the epistatic allele is recessive then

A

Two copies of it will mask the expression of the other gene

39
Q

If you cross a homozygous recessive parent with a homozygous dominant parent you will produce what phenotypic ratio

A

9:3:4

40
Q

If the epistatic allele is dominant then having at least one copy of it will

A

Mask the expression of the other gene

41
Q

Crossing a homozygous recessive parent with a homozygous dominant will produce what phenotypic ratio

A

12:3:1

42
Q

What is the observed result

A

The actual result of the experiment

43
Q

What is the expected result

A

The result predicted by the theory

44
Q

What is the critical value

A

the value of chi squared that corresponds to a 0.05 (5%) level of probability that the difference between our observed and expected results is due to chance.

45
Q
A

Biology (13 decks)

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