Chapter 23 Flashcards

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1
Q

What do chromosomes come in?

A

Pairs called homologous chromosomes.

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2
Q

Where are the members of the pairs of homologous chromosomes inherited from?

A

The mother, and the father.

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3
Q

What are some characteristics of homologous pairs?

A

Both members have same length and centromere location, both carry similar types of genes, alternate forms of a gene for a trait are called alleles, and they are always on the same spot.

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4
Q

What are some examples of alleles?

A

Tail length, eye colour.

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5
Q

What is a phenotype?

A

An individual’s actual appearance that includes physical characteristics or metabolic characteristics.

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6
Q

What is a genotype?

A

Alleles carried by the chromosomes that are responsible for a given trait.

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7
Q

How do you symbolize a dominant allele?

A

A capital letter.

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8
Q

How do you symbolize a recessive allele?

A

A lowercase letter.

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9
Q

What is homozygous?

A

If the 2 alleles are the same.

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10
Q

What is heterozygous?

A

If the 2 alleles are different.

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11
Q

How many alleles does a genotype have for a trait?

A

2

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12
Q

How many alleles does a gamete have for a trait?

A

1

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13
Q

A homozygous man with freckles reproduces with a woman without freckles, will their children have freckles?

A

Yes (Ff)

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14
Q

What are the steps used to solve a genetic cross.

A
  1. Determine the genotype of each parent.
  2. List the possible gametes from each parent.
  3. Combine all possible gametes.
  4. Determine the genotypes and phenotypes of all offspring.
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15
Q

Can you determine by observation if an individual expressing dominant trait is homozygous or heterozygous?

A

No.

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16
Q

How are homologous chromosomes inherited?

A

As a pair, one member from each parent.

17
Q

During meiosis, what does each gamete receive?

A

One member of each pair of homologoues.

18
Q

How do homologues separate?

A

Independently.

19
Q

What is the law of independent assortment?

A

Each pair of factors assorts independently. All possible combinations of factors can occur in the gametes.

20
Q

What is a dihybrid cross?

A

Used to test the law of independent assortment.

21
Q

What things are often genetic in origin?

A

Many traits and disorders in humans and other organisms.

22
Q

What are the genetic traits controlled by?

A

A single allele pair on the autosomal chromosomes, any chromosome other than (X or Y).

23
Q

What is pedigree?

A

A chart of family’s history with regard to a particular genetic trait. It is used to determine whether inherited condition is due to autosomal dominant or autosomal recessive allele.

24
Q

What do autosomal recessive disorders require?

A

The inheritance of two recessive alleles to display the disorder.

25
Q

What are some examples of autosomal recessive disorders?

A

Sickle cell disease, cystic fibrosis.

26
Q

What is an example of an autosomal dominant disorder?

A

Huntington disease.

27
Q

Describe incomplete dominance.

A

Occurs when the heterozygote has an intermediate phenotype between the two homozygotes.

28
Q

What is codominance?

A

Occurs when alleles are equally expressed in a heterozygote.

29
Q

What happens when a trait is controlled by multiple alleles?

A

The gene exists in several allelic forms. Each person has only 2 of the possible alleles.

30
Q

When does polygenetic inheritance occur?

A

When a trait is governed by two or more genes.

31
Q

What do dominant alleles have a quantitative effect on?

A

The phenotype, and the effects are additive.

32
Q

What is the result of the quantitative effect from dominant alleles?

A

Continuous variation of phenotypes. Example: skin colour.

33
Q

What is an example of polygenetic inheritance?

A

General size.

34
Q

What can influence the expression of genetic traits?

A

Environmental factors like nutrition or temperature.

35
Q

What are polygenic traits especially influenced by?

A

Environment.