Important Terms

Question 1

pyrimidines

Answer 1

single carbon-nitrogen rings (cytosine-thymine)

Question 2

purines

Answer 2

double carbon-nitrogen rings (adenine-guanine)

Question 3

polypeptides

Answer 3

protein compounds

Question 4

amino acids

Answer 4

building blocks of polypeptides (20 different amino acids)

Question 5

DNA replication

Answer 5

untwisting and unzipping of DNA strand to leave single strands used for template to be replicated

Question 6

DNA polymerase

Answer 6

enzyme which travels along single DNA strand adding the correct nucleotides and checking base pair complements

Question 7

mutation

Answer 7

any alteration of genetic material

Question 8

mutagens

Answer 8

agents known to increase the frequency of mutations (ie: radiation and chemicals such as nitrogen mustard, vinyl chloride, alkylating agents, formaldehyde, and sodium nitrate)

Question 9

transcription

Answer 9

RNA is synthesized from a DNA template, forming messenger RNA (cytosine-uracil)

Question 10

translation

Answer 10

tRNA translates the mRNA into a protein

Question 11

codons

Answer 11

sequence of base pairs (c,u,a,g)

Question 12

gametes

Answer 12

sperm and egg cells
23 chromosomes
haploid
formed from meiosis

Question 13

somatic cells

Answer 13

all cells other than gametes
46 chromosomes
diploid
formed from mitosis and cytokinesis

Question 14

autosomes

Answer 14

first 22 of the 23 pairs of chromosomes
two members of each pair are virtually identical (homologous)

Question 15

sex chromosomes

Answer 15

remaining pair of chromosomes
females (XX)
males (XY)

Question 16

karyotype

Answer 16

display of chromosomes for one person

Question 17

aneuploidy

Answer 17

somatic cell that does not contain a multiple of 23 chromosomes
monosomy (one copy)
trisomy (three copies)

Question 18

nondisjunction

Answer 18

(usual cause of aneuploidy) an error in which homologous chromosomes or sister chromatids fail to separate normally during meiosis or mitosis

Question 19

deletion

Answer 19

a gamete with broken or lost DNA uniting with a normal gamete to form a zygote

Question 20

locus

Answer 20

position of a gene along a chromosome

Question 21

homozygous

Answer 21

when the two alleles at a given locus are identical

Question 22

heterozygous

Answer 22

when the two alleles at a given locus are not identical

Question 23

allele

Answer 23

one of two or more versions of a gene located at the same position on a chromosome
(can be dominant, recessive, or codominant)

Question 24

genotype

Answer 24

the composition of genes at a given locus (what they have)

Question 25

phenotype

Answer 25

the outward appearance of genetics of an organism (what they demonstrate)

Question 26

dominant allele

Answer 26

the allele whose effects are observable

Question 27

recessive allele

Answer 27

the allele whose effects are hidden

Question 28

pedigree

Answer 28

chart that summarizes family relationships and shows which members of a family are affected by a genetic disease

Question 29

proband

Answer 29

first person in the family diagnosed or seen in a clinic (generally the beginning of the pedigree)

Question 30

penetrance

Answer 30

the percentage of individuals with a specific genotype who also express the expected phenotype (has gene for disease but does not express disease, can still pass to children)

Question 31

expressivity

Answer 31

the extent of variation in phenotype associated with a particular genotype
can be caused by modifier genes, environmental factors, or mutations