Genetics Flashcards
G1 phase
- period after cell division and before start of DNA replication
- cells grow and monitor environment to determine whether to initiate another round of cell division
S phase
- period of DNA synthesis
- cells replicate chromosomes
G2 phase
- period between end of DNA replication and start of cell division
- cells check to make sure DNA replicated successfully and make any necessary repairs
M phase
- period of actual cell division
- prophase, metaphase, anaphase, telophase, and cytokinesis
diploid
two copies of each chromosome
haploid
one set of chromosomes
autosomes
chromosomes that do not differ between males and females
sex chromosomes
chromosomes that differ between males and females
euploid
cells with complete number of chromosomes
aneuploid
cells with missing or extra chromosomes
homologous
two copies of a particular chromosome that can have different variants of the same gene
unreplicated chromosome
chromosome with one long strand of DNA double helix
replicated chromosome
chromosome that has been copied and consists of two identical chromatids, each containing one double helix and joined at the centromere
sister chromatids
the two attached, identical copies of a replicated chromosome
mitosis prophase
chromosomes condense; each chromosome consists of a pair of identical sister chromatids joined at the centromere
mitosis metaphase
chromosomes line up at the middle of the cell, along the plane of cell division, pushed and pulled by microtubules of the spindle apparatus
mitosis anaphase
sister chromatids separate and migrate towards opposite ends of the cell
mitosis telophase
chromatids cluster at opposite ends of the cell and begin to decondense
cytokinesis
the membrane pinches in to divide the two daughter cells
Mendel’s Law of Independent Action
all possible combinations of maternal and paternal chromosomes are possible in the two daughter cells
prokaryote genome
usually packed into one circular chromosome consisting of circular DNA molecule of few million base pairs (Mbp)
eukaryote genome
packaged into multiple linear chromosomes, each consisting of a linear DNA molecule of tens or hundreds of Mbp
chromosome number (N)
the number of chromosomes in a haploid cell, or gamete (sperm or egg cell)
particulate inheritance
the idea that hereditary elements are passed on in discrete units rather than “blended” together at each new generation
gene
- a hereditary factor that determines (or influences) a particular trait
- comprised of a specific DNA sequence and is located on a specific region of a specific chromosome called genetic locus
allele
a particular variant of a gene
genotype
the particular collection of alleles found in its DNA
homozygous
two of the same alleles for a particular gene
heterozygous
two different alleles for a particular gene
phenotype
- observable traits
- can have a heterozygous at a particular locus but have a phenotype that looks like only one of the two alleles due to dominance/recessiveness
dominant allele
produces its phenotype whether the organism is homozygous or heterozygous at that locus
recessive allele
produces its phenotype only when homozygous at the locus; its phenotype is masked if the locus is heterozygous
sex linkage
inheritance of genes of sex chromosomes (X and Y)
genetic linkage
the genes controlling two different traits are located near each other on the same chromosome
genetic recombination
new combinations of alleles on chromosome
Mendelian traits
- single gene
- dominant/recessive inheritance
non-Mendelian traits
anything other than Mendelian traits
differentiate
to become specialized by making different sets of proteins
transcriptional control
whether and how much a gene is transcribed into mRNA
translational control
whether and how much a gene is translated into protein
post-translational control
whether the protein is in an active or inactive form, and whether the protein is stable or degraded
positive regulation
turning on gene expression
negative regulation
turning off gene regulation
co-regulation
turning multiple genes on or off together
promoters
- sites in DNA where RNA polymerase binds to initiate transcription
- contain binding sites for transcription factors
transcription factors
DNA-binding proteins that help recruit or repel DNA polymerase
regulatory element
a DNA sequence that certain transcription factors recognize and bind to in order to recruit or repel RNA polymerase
constitutively expressed
genes always transcribed
operon
two or more functionally related genes transcribed together from single promoter into one long mRNA
lacZ
encodes the enzyme beta-galactosidase, which cleaves lactose into glucose and galactose
lacY
encodes permease, a membrane protein for facilitated diffusion of lactose into the cell
lacA
encodes transacetylase, an enzyme that modifies lactose
C-value paradox
the amount of DNA in a haploid genome (the 1C value) does not seem to correspond strongly to the complexity of an organism, and 1C values can be extremely variable
introns
“intervening” sequences in genes that do not code for proteins
exons
the sequence of DNA present in mature messenger RNA, some of which encodes the amino acids of a protein
principle of segregation
two alleles for a particular trait are segregated into different gametes
principle of independent assortment
alleles for different traits are segregated independently
