7A - Inheritance Flashcards

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1
Q

What does ‘codes for’ mean?

A

Contains the instructions for.

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2
Q

Define gene:

A

A sequence of bases on a DNA molecule that codes for a protein (polypeptide), which results in a characteristic, e.g. a gene for eye colour.

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3
Q

Define allele:

A

A different version of a gene. There can be many different alleles of a single gene, but most plants and animals, including humans, only carry two alleles of each gene, one from each parent. The order of bases in each allele is slightly different - they code for different versions of the same characteristic.

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4
Q

Define genotype:

A

The genetic constitution of an organism - the alleles an organism has.

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5
Q

Define phenotype:

A

The expression of the genetic constitution and its interaction with the environment - an organism’s characteristics.

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6
Q

Define dominant:

A

An allele whose characteristic appears in the phenotype even when there’s only one copy. Dominant alleles are shown by a capital letter.

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7
Q

Define recessive:

A

An allele whose characteristic only appears in the phenotype if two copies are present. Recessive alleles are shown by a lower case letter.

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8
Q

Define codominant:

A

Alleles that are both expressed in the phenotype - neither one is recessive.

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9
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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10
Q

Define homozygote:

A

An organism that carries two copies of the same allele.

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11
Q

Define heterozygote:

A

An organism that carries two different alleles.

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12
Q

Define carrier:

A

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

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13
Q

What do genetic diagrams show?

A

The possible genotypes of offspring.

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14
Q

Are human haploid or diploid organisms?

A

Diploid.

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15
Q

What does diploid mean?

A

Has two sets of chromosomes so have 2 alleles for each gene.

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16
Q

How many alleles for each gene do gametes have?

A

Only 1.

17
Q

What is monohybrid inheritance?

A

The inheritance of a characteristic controlled by a single gene.

18
Q

Whenever you do a monohybrid cross with 2 heterozygous parents, what ratio of dominant:recessive characteristic do you get?

A

3:1

19
Q

What does a dihybrid cross show you?

A

How 2 different genes are inherited at the same time.

20
Q

What is the phenotypic ratio?

A

The ratio of different phenotypes in offspring.

21
Q

What is the phenotypic ratio in the F1 generation in a monohybrid cross?

A

All heterozygous offspring (e.g. Rr).

22
Q

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

A

3:1

dominant : recessive

23
Q

What is the phenotypic ratio in the F1 generation in a dihybrid cross?

A

All heterozygous offspring (e.g. RrYy).

24
Q

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

A

9:3:3:1

dominant both : dominant 1st recessive 2nd : recessive 1st dominant 2nd : recessive both

25
Q

What is the phenotypic ratio in the F1 generation in a codominant cross?

A

All heterozygous offspring.

26
Q

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

A

1:2:1

homozygous for one allele : heterozygous for the other allele.

27
Q

What are the 3 main reasons why the phenotypic ratio is different from what is expected?

A
  • Sex linkage.
  • Autosomal linkage.
  • Epistasis.
28
Q

Explain the dominant and recessive alleles in blood groups

A

Io (blood group O) is recessive.

IA (blood group A) and IB (blood group B) are codominant.

29
Q

Haploid

A

1 set of chromosomes.

30
Q

Diploid

A

2 sets of chromosomes.

31
Q

Polyploid

A

Many set of chromosomes (>2).

32
Q

Codominant

A

When two/both alleles mask the expression of other/both are expressed.

33
Q

Homologous chromosomes

A

Pairs of chromosomes with the same genetic sequence and loci.

34
Q

Monohybrid inheritance

A

The study of the inheritance of alleles for one gene.

35
Q

Dihybrid inheritance

A

The study of the inheritance of alleles for 2 genes at the same time.