Genetics final exam terms

Nondisjunction

when chromosomes or chromatids fail to separate and segregate

Oogenesis

egg production

Oogonia

the cells from which the eggs are developed

Primary oocytes

diploid cells that undergo meiosis 1 to produce a secondary oocyte and the first polar body

Secondary oocytes

a haploid cell resulting from meiosis 1 in oogenesis; it will undergo meiosis 2 if fertilized

First polar body

a small cell containing little cytoplasm produced during oogenesis; it does NOT develop into an egg

Mature ovum

a mature female gamete; a fertilized egg

Second polar body

a small cell produced during meiosis 2 in oogenesis; it is a nonfunctional waste product

Spermatogenesis

sperm production

Spermatogonia

the cells from which the sperms are developed

Primary spermatocytes

diploid cells that undergo meiosis 1 to produce secondary spermatocytes

Secondary spermatocytes

haploid cells that undergo meiosis 2 to produce spermatids

Spermatids

haploid cells that differentiate into sperm

Sperm

mature male gamete

Law of independent assortment

The alleles of one gene move into different gametes independently of how the alleles of another gene move into different gametes.

Hemizgous

having only one copy of a gene or DNA sequence in diploid cells; males are ______ for genes on the X chromosome

Silent mutation

change in base that does not change encoded amino acid, so no change in protein

Missense mutation

change in base that changes the encoded amino acid

Nonsense mutation

change in base that changes an amino acid-encoding codon to a stop codon: results in a truncated (shortened) protein

Frameshift mutation

insertion or deletion of base(s) that change the “reading frame” for translation; will change all the encoded amino acids “downstream” of the insertion/deletion (unless insertion or deletion is a multiple of 3 bases

Conservative missense mutation

chemical properties of new amino acid are similar to original amino acid; less likely to have a significant effect on protein function

Nonconservative missense mutation

chemical properties of new amino acid are different than orgincal amino acid; more likely to have a significant effect on protein function

Regulatory mutation

change in base(s) of DNA in promoter of a gene or in sequences associated with the promoter of gene (enhancer, silencers)

Loss-of-function mutation

activity of encoded protein is reduced or absent

Null mutation (amorphic mutation)

encoded protein has no activity

Hypomorphic mutation

encoded protein has reduced activity

Gain-of-function mutation

activity of encoded protein is increased or different

Hypermorphic mutation

more protein produced (regulatory mutation) or changed protein has a higher level of activity; generate more protein or the same amount of a more active protein

Neomorphic mutation

encoded protein has a new or different activity; generate protein with a NEW or DIFFERENT function or that is expressed ectopically

Haploinsufficieny

in a heterozygote for a loss-of-function allele, one wild type copy of gene doesn’t produce enough activity protein

Aneuploidy

There is an abnormal number of chromosomes; either 1 extra or 1 less

Trisomic

gamete will have an extra chromosome

Monosomic

gamete is missing a chromosome

Triploidy

a cell with three sets of chromosomes

Mendel’s law of segregation

alleles of a gene segregate into separate gametes

X-link

A gene located on the X chromosome

Y-link

A gene located on the Y chromosome

Sexual dimorphism

distinct difference in size or appearance between the sexes of an animal in addition to difference in the sexual organs themselves

Crisscross inheritance

daughters will have the phenotype of their father and sons will have the phenotype of their mothers

Mutation

change in DNA base sequence

Forward mutation

change of a wild type allele to a mutant allele

Reverse mutation

change of a mutant allele to a wild type allele

Depurination

loss of a purine base from a nuc

Deamination

loss of an amino group from a base

Ectopic expression

expression of a gene or protein at an inappropriate time or in an inappropriate place

Transposable elements (TEs)/ Transposons

DNA segments with repetitive sequence that can move from one location in the genome to another

Alkyltransferase

enzyme that removes alkyl groups attatched to DNA bases

Photolyase

enzyme that breaks covalent bonds of thymidine dimers (not found in humans)

Mismatch repair

Detects and corrects errors where the wrong base is inserted in the new strand during DNA replication

Nick

a break in the bond between one nucleotide and the next

Exonuclease

breaks down nucleic acid one nucleotide at a time

AP site

a location in DNA (also in RNA but much less likely) that has neither a purine nor a pyrimidine base, either spontaneously or due to DNA damage.

AP endonuclease

Enzymes that cleave the bonds between nucleotides

Homology dependent repair

Both base and nucleotide excision repair; require that the other strand is correct and intact, since the DNA polymerase is going to go in and read the other strand so that it knows what the proper nucleotides is put there

Restriction Endonucleases

enzymes that cleave DNA at sequence-specific sites

Palindromic sequence

a sequence that reads the same forward as backward

Blunt end cleaver/enzyme

Cleaves DNA in the middle of the strand; there’s no single strand overhang; no sticky ends are created

Resolution

how big a difference in DNA fragments need to be in order for them to separate on the gel.

cDNA

DNA copy of mRNA (reverse transcription PCR)

Molecular cloning

the isolation and amplification of a specific DNA fragment

Gel Electrophoresis

A Laboratory technique used to separate biomolecules like DNA, RNA, or proteins based on their size and charge

Polymerase Chain Reactio (PCR)

A technique used to create millions or billions of copies of a specific DNA segment from a small initial sample

X-chromosome inactivation (or X-inactivation)

a crucial biological process in mammals where one of the two X chromosomes in females is ______ to ensure equal gene dosage between males and females

signal transduction cascade

one molecule gets activated and it activates another molecule that activates another molecule and then eventually one of the activated molecules will either activate a transcription factor (which will either turn off or turn on, or change the level of expression of a certain gene) or activate certain enzymes (which produce certain products that weren’t being produced before)

Signaling molecules

molecules secreted by cells or found on adjacent cells that stimulate or inhibit proliferation of receiving cell

Receptors

bind to, and activated by, signaling molecules; each composed of a signal-binding site outside the cell, a transmembrane segment, and an intracellular domain

Signal transducer

Transmit signals from receptor to target molecules in cell; located in cytoplasm

Transcription factor

activate or repress expression of specific genes to either promote or inhibit cell proliferation

autocrine signaling

when a cell releases a signal and also responds to that signal because it has a receptor for that same signal

contact inhibition

prevents cells from continuing through the cell cycle to move into G0

Apoptosis

programmed cell death

invasion

tumor cells can move into surrounding tissue

metastasis

once tumor cells break through the basemnt membrane they may get into blood vessels and be carrieed to, and grow in, other parts of the body

angiogenesis

the formation of new blood vessels from pre-existing ones

Oncogene

a mutated version of a gene that leads to a hyperactive protein or an overexpressed protein that induces excessive cell proliferation

proto-oncogene

a gene that is required during development for promoting cell division; normal non-mutated form

Tumor suppressor gene

normal gene that encodes a protein that inhibits or prevents cancerous growth

cell proliferation

cell moving all the way through the cell cycle, from G1 to S to G2 into M-phase, mitosis, and cytokinesis producing 2 daughter cells

syntenic genes

genes located on the same chromosome

terminalization

movement of chiasmata towards telomeres (ends of chromosomes)

recombination

the exchange of genetic material between DNA molecules, resulting in new combinations of alleles

hotspot

regions of the chromosome in which crossovers are favored

recombination deserts

regions of a chromosome in which there is little crossing over

endocytosis

a cellular process where a cell engulfs external materials by invaginating its cell membrane to form a vesicle

retrovirus

A type of virus that has RNA instead of DNA as its genetic material; INSERTED into the host genome

adeno-associated virus

a small, non-pathogenic, single-stranded DNA virus that is widely used as a gene therapy delivery vector; DOES NOT integrate into the host chromosomes

reverse transcription

takes RNA and converts it to DNA

somatic cell gene therapy

involves introducing new or modified genes into an individual's somatic cells

Germline Gene therapy

modifies genes in reproductive cells (sperm or eggs) or in early embryos, making these changes inheritable by all offspring

gene “editing” by CRISPR/Cas9

a revolutionary gene-editing technology that allows scientists to precisely modify DNA sequences in living organisms

Knocking out

removing part of the gene

knock-in

adding/swapping out the old sequence for a new sequence, changing the actual sequence of the gene to make it do what we want it to do

phenotype

an observable charateristic of an individual

genotype

the pair of alleles for a gene (or for each of several genes) in an individual

homozygous

having two IDENTICAL alleles for a gene

heterozygous

having two DIFFERENT alleles for a gene

polygenic

many traits are determined by SERVAL genes; these traits don’t show simple Mendelian inheritance patterns

monogenic

determined by a single gene

pleiotropy

a gene may affect several traits

incomplete dominance

heterozygote has a phenotype intermediate between two homozygotes