Inheritance (3.4, 10.2) Flashcards

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1
Q

What concepts did Gregor Mendel discover and how did he discover these?

A

The law of allele segregation, the principle of dominance and independent assortment. He discovered these concepts by performing experiments on pea plants.

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2
Q

Phenotype

A

A structure, process, behaviour or feature of an organism that is determined by its genotype. Observable characteristics.

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3
Q

Genotype

A

An organism’s genetic makeup.

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4
Q

Heterozygous

A

Two different alleles eg. Tt

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5
Q

Homozygous

A

Identical copies of the allele eg. TT or tt

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6
Q

1st filial

A

The heterozygous (Tt) offspring of a cross between two purebred parents (eg. TT and tt).

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7
Q

2nd filial

A

The offspring of a cross between two 1st filial offspring.

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8
Q

What is a Punnett square?

A

A predicted ratio for all possible allele combinations for potential offspring of one gene.

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9
Q

What is a test cross used for?

A

To tell if the dominant phenotype is homozygous (eg. TT) or heterozygous (eg. Tt). A plant w the dominant phenotype is mated with a homozygous recessive plant.

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10
Q

How is a dihybrid test cross carried out?

A

An unknown genotype is mated with a known homozygous recessive. If the unknown parent is homozygous dominant (AABB) all offspring will express the dominant phenotype. If the unknown parent is heterozygous (AaBb) half the offspring should be dominant and half recessive.

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11
Q

What is incomplete dominance?

A

When one allele is not completely dominant over the other. The heterozygote is a mixture of the two alleles eg. a pink flower formed by a red flower crossed with a white flower.

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12
Q

What is co-dominance?

A

When both alleles are independently and equally expressed in the heterozygote. Eg. a mixture of red and white hairs NOT pink hair

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13
Q

Define the term lethal alleles

A

Lethal alleles are gene mutations that result in a gene product that is non functional and affects the organisms survival.

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14
Q

What are the human ABO blood grouping genotypes?

A

A = IAIA or IAi
B = IBIB or IBi
AB = IAIB
O = ii

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15
Q

What does homogametic mean?

A

Two similar sex chromosomes. Eg. Females are XX

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16
Q

What does heterogametic mean?

A

Two unlike sex chromosomes. Eg. Males are XY

17
Q

What is sex determination based on?

A

The presence or absence of the Y chromosome.

18
Q

Why are most sex-linked conditions usually X-linked?

A

The Y chromosome is much shorter than the X chromosome. Therefore it has no corresponding gene to a faulty gene on the X, so cannot mask the effect.

19
Q

Who are the carriers for X-linked conditions?

A

Females, as they can be heterozygous carriers.

20
Q

Define sex linkage

A

When a gene controlling a characteristic is located on a sex chromosome (can be X or Y).

21
Q

What are linked genes?

A

Groups of genes that are on the same chromosome and move together during meiosis (i.e. don’t independently assort).

22
Q

Why are linked gene-phenotype ratios different to non-linked gene-phenotype ratios?

A

Because the phenotype ratio for linked genes will be closer to a monohybrid cross as the two genes are inherited as a single unit.

23
Q

What is the effect of crossing over on linked genes?

A

Crossing over occurs in Prophase I of Meiosis. Homologous pairs of sister chromatids undergo synapsis where they line up side by side. During synapsis, the chromatids may tangle (chiasmata formation) and exchange pieces of DNA (this is coined crossing over). If linked genes become separated by a chiasma an exchange of alleles will occur between non-sister chromatids causing the formation of new allele combinations different to those of the parents.

24
Q

What is the purpose of a Chi-squared table?

A

To determine whether the difference between an observed and expected frequency distribution is statistically significant.

25
Q

Define polygenic traits

A

Characteristics controlled by two or more genes.