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Biology > 8.1 > Flashcards

8.1 Flashcards

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1
Q

why is genetic variation important

A

variation that arises as a result of genetic variation is key to survival and evolution of individuals

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2
Q

what is independent/random assortment

A

components of the chromosome pairs from father and mother are distributed into gametes randomly so any number of your 23 chromosomes could come from your maternal or paternal chromosomes introducing considerable genetic variation

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3
Q

when does crossing over occur

A

meiosis 1 - prophase 1

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4
Q

what is crossing over (recombination)

A

large multi-enzyme complexes cut and join parts of the maternal and paternal chromatids together at the chiasmata to exchange genetic material leading to genetic variation as new combinations of alleles arise

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5
Q

what is a gene/point mutation

A

miscopying of just one or a small number of nucleotides

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6
Q

what is substitution

A

one base is substituted for another

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7
Q

what is deletion

A

a base is completely lost in the sequence

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8
Q

what is insertion

A

an extra base is added to the sequence

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9
Q

what is chromosomal mutation

A

changes in the positions of genes within the chromosomes or entire chromosome is lost or duplicated during meiosis

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10
Q

define phenotype

A

the physical and chemical characteristics that make up the appearance of an organism

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11
Q

what is a gene locus

A

specific site of a gene

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12
Q

what is an allele

A

different versions of a gene

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13
Q

what does polygenic mean

A

phenotype traits are determined by several interacting genes

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14
Q

what is a test cross

A

individual is crossed with a homozygous recessive individual to reveal the parental phenotype

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15
Q

why the ratios predicted by genetic cross not be represented in the population

A
  • combination of alleles in each gamete is completely random
  • some offspring die before they can be sampled (seeds don’t germinate, embryos miscarry)
  • inefficient sampling techniques
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16
Q

what is the law of segregation

A

Mendels law which states that one unit or allele for each trait is inherited from each parent to give two alleles for each trait, the segregation of alleles in each pair takes place when the gametes are formed and some alleles code for phenotypes that are dominant over others

17
Q

what is the law of independent assortment

A

Mendels law that different traits are inherited independently of each other which means that inheritance of alleles for one phenotype has nothing to do with the inheritance of alleles of another characteristic

18
Q

what does it mean if a gene has multiple alleles

A

there are more than two possible variants at a particular locus

19
Q

what is codominance

A

both alleles are expressed and the proteins they code for act together without mixing to produce a given phenotype

20
Q

what is a digenic (dihybrid) cross

A

representation of breeding experiments involving the inheritance of two pairs of contrasting characteristics at the same time

21
Q

what are recombinant phenotypes

A

offspring that have different phenotypes to their parents as a result of recombination of the chromosomes during sexual reproduction

22
Q

what is gene linkage

A

when genes for two characteristics are found on the same chromosome and are close together so they are linked and inherited as a single unit

23
Q

what is homogametic

A

individual produces gametes that only contain one type of sex chromosome

24
Q

what is heterogametic

A

individual produces gametes that contain two different types of sex chromosome

25
Q

what is sex linkage

A

genes that are carried on the sex chromosome

26
Q

what is a sex linked disease

A

a genetic disease that results from a mutated gene carried on the sex chromosome

27
Q

what is haemophilia

A

a sex linked genetic disease in which one of the factors needed for clotting the blood is not made in the body

Biology (33 decks)

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