ch 12 - Genetics and Evolution Flashcards Preview

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Flashcards in ch 12 - Genetics and Evolution Deck (72)
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1

chromosomes

organization of all genes and a large supply of noncoding DNA

2

alleles

alternative forms of genes

3

genotype

genetic combination possessed by an individual

4

phenotype

manifestation of a given genotype as an observable trait

5

homologues

two copies of a chromosome possessed by each human and applicable to every chromosome except the male sex chromosomes XY.

6

locus

location of a gene on a chromosome; used to describe a gene

7

hemizygous

genotype description in which only one allele is present for a given gene

8

complete dominance

only one dominant and one recessive allele exist for a given gene; presence of one dominant allele will mask the recessive allele

9

codominance

when more than one dominant allele exists for a given gene. Both genes are expressed (AB blood type)

10

incomplete dominance

when a heterozygote expresses a phenotype that is intermediate between the two homozygous genotypes. Red flower, white flower = pink flower

11

penetrance

population measure defined as the proportion of individuals in the population carrying the allele who actually express the phenotype

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full penetrance

100% of inds with the allele show phenotype

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expressivity

varying phenotypes despite identical genotypes

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constant expressivity

all inds with a given genotype express the same phenotype

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variable expressivity

inds with same genotype may have different phenotypes

16

Mendel's First law (of segregation)

-genes exist in alternative forms (alleles); -organism has 2 alleles for each gene, one inherited from each parent; -2 alleles segregate during meiosis, resulting in gametes that carry only one allele for any inherited trait; -if two alleles for an organism are different, only one will be fully expressed and the other will be silent

17

Mendel's Second Law: Law of Independent Assortment

states that inheritance of one gene does not affect the inheritance of another gene

18

mutation

change in DNA sequence which results in mutant allele

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wild-type

alleles that are considered normal to natural and are ubiquitous in the study population

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mutagens

substances that can cause mutations

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transposons

elements that can insert and remove themselves from the genome and can cause mutations

22

Point mutations review

occur when one nucleotide in DNA (A, C, T, or G) is swapped for another. Categories are silent, missense or nonsense

23

silent mutations

occur when the change in nucleotide has no effect on final protein synthesized from the gene; most commonly when the change is at the third nucleotide in the codon because of the degeneracy (wobble) in genetic code

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missense mutations

occur when the change in nucleotide results in substituting one amino acid for another in the final protein

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nonsense mutations

occur when change in nucleotide results in substituting a stop codon for an amino acid in the final protein

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Frameshift mutations

occur when nucleotides are inserted into or deleted from the genome shifting the reading frame; categorized as insertion or deletion mutations

27

chromosomal mutations

larger-scale mutations than codon mutations in which large segments of DNA are affected

28

deletion mutations of chromosomes

occur when a large segment of DNA is lost from a chromosome

29

duplication mutations of chromosomes

occur when a segment of DNA is copied multiple times in the genome

30

Inversion mutations of chromosomes

occur when a segment of DNA is reversed within the chromosome