Test 2 Vocab

pedigree

a depiction of a family's history with respect to the inheritance of a specific trait

carrier

someone who has one allele but no trait

monozygotic twins (identical)

when a single sperm fertilizes a single egg, but developing embryo splits into two

dizygotic twins (fraternal)

two sperm cells fertilizes two eggs, each develops into independent embryos

concordance

the percentage of twin pairs in which both individuals show the characteristic

amniocentesis

procedure used to obtain fetal cells in the amniotic fluid for genetic testing. This can be performed in the 15-18th week of pregnancy

chorionic villus sampling

procedure used to obtain cells from the chorion(outer layer of the placenta). This can be performed in the 10-12th week of pregnancy

noninvasive prenatal screening (NIPS)

procedure when a blood sample is taken from the mother, and certain levels of proteins and hormones can be measured. Can detect fetus DNA without affecting the fetus' development

incidental findings

can reveal underlying health issues in the mother, discovered accidentally

nucleotide

the sugar-phosphate and nitrogenous base that make up DNA molecules

deoxyribose

the sugar that is used in DNA nucleotides

phosphodiester bonds

the bonds between the 3’ OH of one nucleotide and the 5’ PO₄ of the next that hold DNA or RNA together; these bonds create the angles that produce right-handed turns in the helix

topoisomerase

the enzyme that introduces supercoils into (non-eukaryotic) DNA strands

chromatin

the packaged form of DNA that is formed with the help of proteins

euchromatin

a type of chromatin in which the DNA is less condensed and is open for transcription

heterochromatin

a type of chromatin in which the DNA is highly condensed and no transcription can take place, there are “regions of inactivity”

histone core

an 8-protein center that the DNA is wound around, which contains two copies each of H2A, H2B, H3, and H4

nucleosome

the combination of DNA and histone core, kept together by histone H1

nucleases

enzymes that digest DNA

C value

the amount of DNA per cell in an organism

mutation

any heritable change in the genetic material/sequence; this can pass on to the next generation and/or to daughter cells

somatic mutations

these occur in cells of organs and tissues that will not produce gametes, at some point during development; these are only passed to cells within the organism

germ-line mutations

these occur in the progenitor cells that form gametes, and are typically a result of mutations within reproductive organs; these are passed down to individuals in the next generation

point mutations

single base changes, either as substitutions or indels

base substitutions

can be either transitions or transversions

transitions

base substitutions between a purine and a purine or a pyrimidine and a pyrimidine

transversions

base substitutions between a purine and a pyrimidine (or vice versa)

indels

insertions and deletions; the addition or removing of a nucleotide; can produce frameshift mutations

frameshifts

the movement of nucleotides upstream or downstream that change the codons and resulting proteins (indels of multiples of 3 do not cause these)

anticipation

when the severity (of a disease/mutation) increases with each generation

silent mutation

result of a base substitution, where a codon is changed to another codon for the same amino acid result

missense mutation

result of a base substitution, where a codon is changed to encode a different amino acid; two types of these, conservative or nonconservative

conservative missense

when a missense mutation results in a codon that encode for an amino acid with the same chemical properties (polarity, charge)

nonconservative missense

when a missense mutation results in a codon that encode for an amino acid with different chemical properties (polarity, charge)

nonsense mutation

result of a base substitution, where a codon is changed for a stop codon

loss of function mutations

when the mutant protein is defective/not produced; typically recessive

gain of function mutations

when the mutant protein has a new function/is produced in abnormal place/time during development; usually dominant, typically earlier in development

conditional mutations

when the mutant protein is only abnormal under certain environmental conditions; the altered protein sequence interacts more in certain conditions

lethal mutations

a mutant phenotype is shown in the viable heterozygote, but the homozygous state do not live, causes premature death; technically dominant traits

reversions

a mutation that changes a forward mutation back to WT

suppressor mutations

suppresses the effect of an earlier mutation at a different region

intragenic suppressor mutations

suppresses the effect of an earlier mutation within the same gene

intergenic suppressor mutations

suppresses the effect of an earlier mutation in another gene

mutation rate

the probability that a mutation will occur in that gene in a single generation

mutation frequency

the incidence of mutation in a particular gene within a population (how common the mutation is, eg. 1 in 200,000 individuals)

spontaneous mutations

occur independently of an external agent; due to a molecule or chemical inside cells and occur naturally

induced mutations

generated by an external agent; due to molecules originating outside the cells that come into the cell

depurination

destroys covalent bond and removes the base, but leaves the backbone intact, results in the loss of a purine base (A or G), most common form spontaneous DNA degradation; typically replaced with an adenosine

deamination

the removal of an amino group from a base; spontaneous mutation due to water or chemical mutagenesis. can produce a transition mutation, from C:G to T:A, C converts to U (U pairs with A)

induced mutations

chemical mutagens that alter existing bases and produce transition mutations

intercalating agents

molecules that are complex, flattened rings that can get in between 2 bases of DNA and disrupt DNA polymerase

pyrimidine dimers

crosslinks in adjacent pyrimidines, primarily occur between adjacent Ts, producing thymine dimers, creates a buckle in DNA backbone and blocks replication

transposition

encode their own movement in the genome

linkage

the inheritance of genes on the same chromosome

coupling (cis) configurations

both dominant alleles on one chromosome and both recessive alleles on the other

repulsion (trans) configurations

one dominant allele and one recessive allele on each chromosome

recombination frequency

(number of recombinant progeny/total number of progeny) x 100

gene maps

the order of genes and the relation/distance between the genes

map units

the distance between genes on chromosomes, equal to 1% recombination