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biology > Inherited change > Flashcards

Inherited change Flashcards

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AP® Biology flashcards Biology 101 flashcards
1
Q

What is a gene?

A

A length of DNA that codes for one polypeptide

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2
Q

What is a locus?

A

The position of a gene on a chromosome

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3
Q

What is an allele?

A

Alternative versions of a gene. (If more than 2, they are multiple alleles).

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4
Q

What is the genotype?

A

The combination of alleles possessed by an organism

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5
Q

What is the phenotype?

A

The observable characteristics of an organism due to a combination of genotype and the environment

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6
Q

What is meant by homozygous?

A

When a genotype has the same 2 alleles of a gene, making the organism a homozygote

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7
Q

What is meant by heterozygous?

A

When a genotype has different 2 alleles of a gene, making the organism a heterozygote

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8
Q

What is meant by dominant?

A

An allele that is always expressed in the phenotype

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9
Q

What is meant by recessive?

A

An allele that is only expressed in the phenotype of a homozygote

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10
Q

What is meant by codominant?

A

Alleles which are both expressed in the phenotype (if they occur together)

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11
Q

How are new genetic combinations created in meiosis?

A

Homologous chromosomes pair up and swap alleles during crossing over

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12
Q

What type of cells does meiosis produce?

A

Gametes, which are genetically different

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13
Q

What does a monohybrid cross involve?

A

The inheritance of one gene

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14
Q

When is a characteristic sex-linked?

A

If the gene that codes for it is located on one of the sex chromosomes (X or Y)

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15
Q

What sex chromosomes do females have?

A

XX

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16
Q

What sex chromosomes do males have?

A

XY

17
Q

Why are males more susceptible to genetic disorders than females?

A

Because the Y chromosome is so small that it contains very few genes, so most sex-linked genes are located on the X chromosome. Due to males only having 1 X chromosome, if they carry a defective recessive allele, this WILL affect the phenotype as it is the only allele of the gene present.

18
Q

What happens if a female has a defective recessive allele of a gene on 1 X chromosome?

A

She will NOT suffer from the genetic disorder as long as her second X chromosome carries a normal dominant allele of that gene, She is called a carrier of the genetic disorder, due to being heterozygous.

19
Q

What type of alleles are most genetic disorders caused by?

A

Recessive alleles

20
Q

What would be evidence on a pedigree diagram that a disorder is recessive?

A

If 2 unaffected parents have an affected child (don’t forget to quote any numbers)

21
Q

What does a dihybrid cross involve?

A

The inheritance of 2 different genes

22
Q

What are the 3 types of dihybrid cross?

A

-Unlinked genes
-Epistasis
-Autosomal linked genes

23
Q

What do unlinked genes involve?

A

2 different genes on 2 different chromosomes that control 2 different characteristics

24
Q

What does epistasis involve?

A

2 different genes on 2 different chromosomes that control the same characteristic

25
Q

What do autosomal linked genes involve?

A

2 different genes on the same chromosome that control 2 different characteristics

26
Q

How is a Barr body formed?

A

Early in a female’s development, one X chromosome is unactivated, which then supercoils to form the Barr body.

27
Q

What is a Barr body?

A

A condensed, inactive X chromosome

28
Q

What are unlinked genes caused by?

A

The independent segregation which occurs in meiosis

29
Q

What is epistasis?

A

The interaction of different genes so that one gene controls the expression of alleles of another gene

30
Q

What are “linked” genes?

A

Genes for different characteristics that are located on the same chromosome

31
Q

What is autosomal linkage?

A

When 2 genes are located on the same autosome (non-sex chromosome), so are inherited together

32
Q

How does linkage with crossing-over alter the ratio of the genotypes and phenotypes of the offspring?

A

It results in more of 2 phenotypes than expected and less of the other 2 phenotypes

biology (18 decks)

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