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A2 Biology > Inherited Change > Flashcards

Inherited Change Flashcards

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AP® Biology flashcards Biology 101 flashcards
1
Q

What is genotype?

A

The genetic constitution of an organism. It describes all the alleles that an organism has.

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2
Q

What is phenotype?

A

The characteristics of an organism resulting from the expression of its genotype and environment

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3
Q

What is a gene?

A

A sequence of nucleotides along a short length of DNA that codes for a polypeptide

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4
Q

What is an allele?

A

An alternative form of a gene

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5
Q

What is homozygous?

A

When the alleles of a particular gene are identical

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6
Q

What is heterozygous?

A

When the alleles of a particular gene are different

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7
Q

What is recessive?

A

Two copies of the allele needed for the characteristic to be expressed in the phenotype

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8
Q

What is dominant?

A

Only one copy of the allele needed for the characteristic to be expressed in the phenotype

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9
Q

What is co-dominance?

A

Where both alleles contribute to the phenotype

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10
Q

What is a test cross?

A

A particular type of cross when an organism of unknown genotype is crossed with a homozygous recessive organism.
It can determine whether an organism is homozygous or heterozygous dominant

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11
Q

Blood type A

A
  • cannot have B or AB blood (anti-b antibodies)
  • can have A or O
  • antigen A and anti-b antibodies
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12
Q

Blood group B

A
  • cannot have A or AB blood
  • can have B or O
  • antigen B and anti-a antibody
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13
Q

Blood group AB

A
  • can have any type of blood, is the universal recipient
  • has no antibodies to react with A or B
  • has antigens A+B and no antibodies
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14
Q

Blood group O

A
  • can have only O blood
  • is universal donor
  • no antigens and both antibodies
  • no antigens for the recipients immune system or reaction against
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15
Q

What is sex-linkage?

A

A gene is described as being sex-linked if it is found on one of the sex chromosomes

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16
Q

What are the sex chromosomes?

A
  • females: XX
  • males: XY
17
Q

Where do sex chromosomes come from?

A
  • Y chromosomes only come from the father
  • X from mother (and father)
18
Q

Why are characteristics from recessive alleles more common in males?

A
  • controlled by recessive alleles on non-homologous portion on the X chromosome will appear more frequently in males
  • this is because there is no homologous portion on the Y chromosome that might have the dominant allele
19
Q

What are autosomes?

A

The remaining 22 pairs of chromosomes (in humans)
Apart from sex chromosomes

20
Q

What is autosomal linkage?

A

If two or more genes are carried on an autosome

21
Q

What is different about alleles when they are autosomally linked?

A

They don’t segregate according to independent assortment

22
Q

When is crossing over least likely to occur on autosomally linked chromosomes?

A

When the genes are closest together

23
Q

What is epistasis?

A
  • arises when the allele of one gene affects/masks the expression of another in the phenotype
24
Q

How can epistasis occur for enzymes?

A
  • if recessive alleles code for non-functional proteins, then the pathway may not be completed
  • the effects of the enzyme cannot be expressed because no pigment can be made
25
Q

What is recessive epistasis?

A
  • two alleles for the masking epistasis gene must be present and so the genotype of the other gene becomes irrelevant
26
Q

What is dominant epistasis?

A
  • the presence of at least one epistasis gene masks the effect of the other gene which becomes irrelevant
27
Q

Why do the results of genetic crosses often differ from predicted results?

A
  • crossing over
  • random fertilisation
  • independent segregation
28
Q

How many different gametes can be produced by meiosis from a cell?

A
  • 2 to the power of how mean sets of genes there are
29
Q

What is the nature of multiple alleles?

A
  • genes may have more than one allele e.g. blood group
  • although there maybe multiple possible alleles- only 2 can be present in an individual (2 homologous chromosomes)

A2 Biology (4 decks)

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