Transmission Genetics And The Sources Of Genetic Variation

Front 1

Amino acids

Back 1

Specified by nucleotide triplets, these molecules are the building blocks of proteins. (p. 187)

Front 2

Chromosomal deletion

Back 2

A mutation involving the loss of a section of a chromosome. (p. 193)

Front 3

Chromosomal duplication

Back 3

A mutation involving the duplication of a section of a chromosome. (p. 192)

Front 4

Cis regulatory elements

Back 4

DNA sequences that modify the expression of other genes that are nearby on the chromosome, often by acting as binding sites for transcription factors. (p. 189)

Front 5

Codominant

Back 5

Two alleles are said to be codominant if both contribute to the phenotype of the heterozygote -- that is, if an A1A2 heterozygote manifests a phenotype intermediate between the A1A1 and A2A2 homozygotes. See also dominant, recessive. (p. 189)

Front 6

Codons

Back 6

A sequence of three consecutive nucleotides specifying an amino acid product. (p. 187)

Front 7

Crossing-over

Back 7

The physical exchange of segments of DNA on homologous chromosomes during meiosis. (p. 190)

Front 8

Dominant

Back 8

An allele A1 is said to be dominant over another allele A2 if its effects on phenotype cover up those of A2 -- that is, if the A1A2 heterozygote manifests the same phenotype as the A1A1 homozygote. (p. 181)

Front 9

Enhancers

Back 9

Regulatory elements that increase the rate of transcription. (p. 189)

Front 10

Exons

Back 10

Stretches of DNA that code for protein products. See also introns. (p. 188)

Front 11

Frameshift mutation

Back 11

A mutation in which the addition or deletion of base pairs causes a shift in reading frame. Unless an addition or deletion involves a number of base pairs that is a multiple of 3, it will cause a frameshift mutation. (p. 192)

Front 12

Gametes

Back 12

The sex cells of an organism. In animals, sperm and eggs are gametes. (p. 181)

Front 13

Gene

Back 13

A sequence of DNA that specifies a functional product. (p. 188)

Front 14

Genotype

Back 14

Either the combination of alleles that an individual has at a given locus, or the combination of alleles that an individual has at all loci. (p. 188)

Front 15

Heterozygotes

Back 15

Individuals with two different alleles at a given locus -- for example, A1A2. (p. 188)

Front 16

Homozygotes

Back 16

Individuals with two copies of the same allele at a given locus -- for example, A1A1 or A2 A2. (p. 188)

Front 17

Introns

Back 17

Noncoding stretches of DNA that interrupt protein-coding regions known as exons and that are excised before translation. (p. 188)

Front 18

Inversion

Back 18

A mutation in which the orientation of a stretch of a chromosome is reversed. (p. 193)

Front 19

Law of independent assortment

Back 19

Mendel's principle stating that which allele is passed down to the next generation at one locus is independent of which allele is passed down at other loci. This law holds only for pairs of unlinked loci, such as loci on different chromosomes. (p. 181)

Front 20

Law of segregation

Back 20

Mendel's principle that each individual (of a diploid species) has two gene copies at each locus and these gene copies segregate during gamete production. Thus, at each locus only one gene copy goes into each gamete, and an offspring receives one gene copy at each locus from each parent. (p. 181)

Front 21

Locus

Back 21

The physical location of a gene on a chromosome. (p. 181)

Front 22

Promoter

Back 22

A short DNA sequence before the transcribed region of a gene, to which the RNA polymerase binds to initiate transcription. (p. 186)

Front 23

Recessive

Back 23

An allele A1 is said to be recessive to another allele A2 if its effects on phenotype are covered up in the heterozygote -- that is, if the A1A2 heterozygote manifests the same phenotype as the A2A2 homozygote. See also dominant. (p. 181)

Front 24

Regulatory elements

Back 24

Stretches of DNA involved in controlling levels of gene expression. (p. 189)

Front 25

Silent mutation

Back 25

A base pair substitution that does not change the amino acid that a codon normally produces. Also known as a silent mutation. (p. 191)

Front 26

Synonymous mutation

Back 26

A base pair substitution that does not change the amino acid that a codon normally produces. Also known as a silent mutation. (p. 191)

Front 27

Trans regulatory elements

Back 27

DNA sequences that modify the expression or activity of genes that are not nearby on the chromosome, often by coding for transcription factors. (p. 189)

Front 28

Transcription

Back 28

The process of copying DNA sequence into a complementary messenger RNA (mRNA). (p. 186)

Front 29

Transition

Back 29

A mutation in which a purine (adenine or guanine) is replaced by a purine, or a pyrimidine (cytosine or thymine) is replaced by a pyrimidine. See also transversion. (p. 191)

Front 30

Transmission genetics

Back 30

The study of the mechanisms by which genes are passed from parents to offspring. (p. 180)

Front 31

Transversion

Back 31

A mutation in which a purine is replaced by a pyrimidine or vice versa. See also transition. (p. 191)