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DNA adduct
attachment of a chemical mutagen to a nitrogenous base
dna replication
process of producing 2 identical copies from one original DNA molecule
5’ → 3’
direction new DNA strand is synthesized in
mutation
change in the DNA sequence
genome
cell’s DNA
mitosis is a type of cell division that promotes growth and tissue repair/ renewal
in adults, most specialized cells have lost the ability to divide - only stem cells can divide
the goal of mitosis is to create 2 cells with identical genetic information
mitosis is like a copy machine
4 key ideas of mitosis
renew the outer layer of skin
example of stem cell function
chromatin
mixture of DNA and proteins that form chromosomes
chromosomes
threadlike structure made of proteins and a single molecule of DNA
homologous chromosomes
chromosomes that have all the same genes but may have different alleles of those genes
chromatid
one of the 2 identical halves of a chromosome
cell cycle
life of a cell from the time its first formed during division of a parent cell until its own division into 2 offspring cells
metabolic activity and growth
G1 phase
duplication of chromosomes (DNA synthesis)
S phase
metabolic activity, growth and preparation for cell division
G2 phase
mitosis and cytokinesis
mitotic phase
mitosis
distribution of chromosomes into identical nuclei
cytokinesis
division of the cytoplasm
centrosome
organize microtubules of the spindle
cell cycle control system
cyclically operating set of molecules in the cell that both triggers and coordinates key events in the cell cycle
cyclins
proteins named for their cyclically fluctuating concentrations in the cell
cyclin dependent kinase
activity rises and falls with changes in concentration of its cyclin partner
maturation promoting factor (MPF)
cyclin-CDK complex that triggers a cell’s past the G2 checkpoint
cancer
disease in which some of the body’s cells grow uncontrollably
tumor supressor genes
normal genes that function to detect errors in DNA replication and respond to either correct them or undergo programmed cell death
proto-oncogenes
normal genes that function to detect and respond to signals that stimulate a cell to divide
heredity
transmission of traits from one generation to the next
variation
the difference in appearance that offspring show from parents and siblings
genetics
scientific study of heredity and variation
genes
hereditary units made of DNA that parents transmit to their offspring
locus
gene’s specific location along a chromosome
gametes
reproductive cells (sperm and eggs)
somatic cells
all cells of the body except gametes
asexual reproduction
single individual passes all of its genes to its offspring via mitosis without the fusion of gametes
clone
group of genetically identical individuals from the same parent
sexual reproduction
2 parents give rise to offspring that have unique combinations of genes inherited from 2 parents
life cycle
generation to generation sequence of stages in the reproductive history of an organism
diploid
containing 2 complete sets of chromosomes, one from each parent
law of segregation
the maternal and paternal copies of a given chromosome or gene separate during meiosis and end up in different gametes at random (with equal probability)
independent assortment
maternal and paternal chromosomes of any homologous pair segregate into gametes independently of all other homologous pairs of chromosomes
crossing over
maternal and paternal chromosomes exchange genetic information during prophase 1
law of segregation
law of independent assortment
crossing over
meiosis is like a slot machine that produces 4 genetically distinct cells
4 key ideas of meiosis
chiasmata
spots where crossing over has just occurred
cohesins
proteins that hold together sister chromatids after duplication
chance of ending up with 1 chromosome x chance of ending up with another chromosome
how do you calculate probaility
meiosis
special type of cell division that reduces the number of chromosome sets from diploid to haploid
metaphase
which phase of meiosis is independent assortment relevant to
independent assortment, crossing over and random fertilization
what 3 mechanisms contribute to genetic variation in sexual life cycles
trait
variant of a character
allele
alternative versions of heritable factors (genes)
multiplication rule
probability that two or more independent events will occur together (this and that)
addition rule
probability that any one of 2 or more mutually exclusive events will occur together
phenotype
appearance of a trait
genotype
genetic makeup of an individual
quantitative characters
characters that vary in a population along a continuum
incomplete dominance
phenotype of F1 hybrids is somewhere between the phenotypes of 2 parents
codominance
2 dominant alleles affect the phenotype in separate distinguishable ways
epistatis
expression of a gene at one locus alters the phenotypic expression of a gene at a second locus
polygenic inheritance
multiple genes affect the phenotype
pleiotrophy
a single gene has effects on multiple phenotypes
chromosome theory of inheritance
mendelian genes have specific loci along chromosomes - chromosomes undergo segregation and independent assortment
sex linked gene
gene located on either sex chromosome
hemizygous
male only needs one copy of an allele for a recessive X linked trait to be expressed
Barr body
inactive X chromosome condenses into during embryonic development
uniparental inheritance
organelle genes are inherited from one parent - ex. human mitochodria are maternally inherited via cytoplasm of the egg
linked genes
genes that are near each other on the same chromosome that deviate from Mendel’s law of independent assortment
aneuploidy
when there is an abnormal number of a particular chromosome
monosomy
(2n-1) chromosomes
trisomy
(2n+1) chromosomes
polyploidy
have multiple complete sets of chromosomes
linkage map
genetic map based on recombination frequencies
nondisjunction
pairs of homologous chromosomes do not separate normally during meiosis
polyploidy (trait)
what is important for plant diversification and speciation
deletion
removal of a chromosome segment
duplication
segment of a chromosome repeated
inversion
reverses a segment within a chromosome
translocation
moves a segment from one chromosome to a non homologous chromosome
helicase
unwinds parental double helix at replication forks
single strand binding protein
binds to and stabilizes single stranded DNA until it used as a template
topoisomerase
relieves overwinding strain ahead of replication forks by breaking, swiveling and rejoining DNA strands
primase
synthesizes an RNA primer at 5’ end of leading strand and at 5’ strand end of each Okasaki fragment of lagging strand
DNA ligase
joins Okazaki fragments of lagging strand, on leading strand, joins 3’ end of DNA that replaces primer to rest of leading strand DNA
RNA directed RNA polymerase (trait)
which enzyme can initiate transcription without a primer
regulation of enzyme activity and regulation of enzyme production
what are 2 ways that cells can control metabolic activity?
RNA polymerase 2
complex of more than 10 proteins in eukaryotic organisms that transcribes genes encoding mRNAs and some non coding mRNA (encodes most protein coding genes) and CANNOT initiate transcription by itself
core promoter
area on genes in eukaryotes where general transcription factors bind to bring RNA polymerase
general transcription factors
bind to promoter on all genes - forms transcription initiation complex
control elements (enhancers)
regions of DNA that can be close or far from core promoter that can bind specific transcription factors
transcription factors
proteins that bind to control elements that function as activators or repressors
DNA binding domain
part of transcription factor protein that interacts with DNA helix (binds to DNA)
activation domain
part of transcription factor protein that interacts with other proteins
protein mediated bending of DNA brings activators (TF) into contact with mediator proteins that interact with general transcription factors at the promoter - this protein- protein interaction positions the transcription initiation complex on the promoter
how do general TFs and TF interact to initiate transcription?
each cell type contains a different group of activators that determine which gene is expressed
how do eukaryotic genes control which genes are expressed during transcription
every gene in the group has shared control elements/ enhancers ex. - Gal4 binds upstream to all genes
how is gene expression coordinated between different genes in eukaryotes?
alternative RNA splicing
different mRNA molecules are produced from the same primary transcript depending on which segments are treated as exons and introns
rate of synthesis (transcription and processing) and rate of degration
what does steady state level of mRNA depend on
steady state level
amount of RNA present at any given point in time
miRNA
short noncoding mRNA that regulate RNA degradation and translation
RISC
miRNA is assembled into this and either cleaves mRNA that is degraded by exonucleases or blocks ribosomes from translating mRNA
genes are organized in operons and have TATA box and tata binding protein, have histones and simplified chromatin, specific transcription factors resemble bacteria TF in structure and action,
what are features of gene expression in archea