Chapter 4 Genes and Cellular Function

deoxyribonucleic acid

long thread-like molecule, 46 DNA molecules (chromosomes) that carry instructions on how to make proteins

nucleotides

monomers of nucleic acids consisting of a sugar, a phosphate, and a nitrogenous base

purines

double ringed nitrogenous base —> adenine and guanine

pyrimidines

single ringed nitrogenous base —> cytosine, thymine, and uracil

base pairs

nitrogenous bases connected by hydrogen bonds

law of complementary base pairing

sequence of one strand determines the sequence of the other

gene

information containing segment of DNA that codes for the production of a molecule of RNA that often synthesizes 1+ proteins

chromatin

fine filament of DNA and histones

histones

proteins DNA winds around made from 8 molecules

sister chromatids

two parallel filaments of identical DNA

centromere

junction of chromatids

kinetochores

protein plaques on each side of centromere

ribonucleic acids

consists of ribose, a nitrogenous base, and phosphate group in a single chain

genome

all DNA in one 23 chromosome set

single-nucleotide polymorphisms

change in a single nucleotide causing all human genetic variation

genomics

comprehensive study of the genome and how genes and ncRNA affect structure and function of organisms

genomic medicine

application of genome knowledge to prediction, diagnosis, and treatment of disease

gene substitution therapy

procedure where cells are removed from patient with genetic disorder, replace defective gene with a normal one, and are reintroduced to the body

proteome

the set of all the different proteins the human body can make

genetic code

system that codes amino acids from the 4 nucleotides

base triplet

3 DNA nucleotides code for one amino acid

codon

3 base sequence of mRNA

stop codons

signal the end of a protein

start codon

AUG codes for methionine and signals the start of making a proteins

messenger RNA

is coded from DNA and codes for the production of protein in the cytoplasm, has a protein cap to leave the nucleus that also tells the ribosome where to begin translation

transcription

occurs in the nucleus, mRNA being coded for from DNA

translation

usually occurs in the cytoplasm, mRNA being read and protein being synthesized

RNA polymerase

binds to the DNA and assembles the pre-mRNA during translation

pre-mRNA

immature mRNA that still contains introns

exons

segments if pre-mRNA that will be translated into protein

introns

segments of pre-mRNA that are removed before translation

alternative splicing

allows one gene to code for more than one protein by having different combinations of exons spliced together

transfer RNA

small RNA that bind to an amino acid and builds the protein chain

anticodon

three nucleotides complementary to a specific codon of mRNA

initiator tRNA

first tRNA to bind to a ribosome at the start of translation that always has UAC anticodon

ribosomes

the readers that facilitated translation made of a small and large subunit that only come together during translation

APE sites

tRNA first binds to A site where the amino acid is accepted, the P site where the growing protein is, and the E site where the tRNA leave

initiation

mRNA enters the cytosol and small subunit binds to a leader sequence of bases near the cap, then finds the start codon, then tRNA with met attaches in the P site and the large subunit joins

elongation

next tRNA arrives in the A site and the amino acid makes a peptide bond with the Met in the P site and then leaves through the E site

termination

stop codon binds release factor in A site instead of tRNA, then protein is released, subunits dissociate

polyribosome

when multiple ribosomes are on the same mRNA at the same time

chaperone

an older protein that binds to a new protein and guides the new protein folding into the proper shape

posttranslational modification

enzymes inn cistern modify protein, ex. remove segments, folding the protein and stabilize with disulfide bridges, adding carbohydrates

transport vesicles

bubble coated in clathrin that takes protein to the golgi

secretory vesicles

golgi vesicle that releases cell products via exocytosis

DNA helicase

enzyme that opens up the double helix exposing the bases

replication fork

the point where DNA is opened up

DNA polymerase

reads the nitrogenous bases and find the complementary base

DNA ligase

joins the segments of DNA by fusing the sugar phosphate backbones

semiconservative replication

each daughter DNA is made from one parental and one new strand of DNA

DNA Damage Response

different ways of correcting DNA replication mistakes, ex. DNA polymerase checks itself via proofreading to catch mismatched base pairs

mutations

changes in DNA structure due to replication errors or from environmental factors, ex. radiation, chemicals, viruses

G1

first gap phase, an interval between cell division and DNA replication where the cell grows and makes proteins lasting about 8-10 hrs

S

synthesis phase where cell replicates centrioles and DNA taking about 6-8 hrs

G2

second gap phase where the cell grows more, makes organelles and enzymes to help with cell division, and checks the DNA for replication mistakes for 4-6 hrs

M

mitotic phase where the cell replicates the nucleus and pinches to form new daughter cells in 1-2 hours

interphase

name for time between M phases, which includes the G1, S and G2 phases

G0 phase

cells that do not divide

mitosis

the division of body cells for growth and repair of an organism excluding sex cells

prophase

chromosomes shorten, nuclear envelope dissolves, spindle fibers push centrioles to the poles and connect to the kinetochore and begin lining up the chromosomes

metaphase

chromosomes are aligned in the center of the cell and the mitotic spindle is formed from the spindle fibers connected to chromosomes and the astral ones anchoring the centriole to the plasma membrane

anaphase

sister chromatids are cleaved at the centromere forming daughter chromosomes and pulled to the poles by motor proteins

telophase

daughter chromosomes cluster at the poles, the rough ER produces a new nuclear envelope and the chromosomes turn back into chromatin, mitotic spindle is broken up

cytokinesis

overlaps with telophase where the cytoplasm is cinched off by myosin pulling on actin microfilaments forming the cleavage furrow in the middle to create the distinct cells

genetic mosaicism

state of the body having different genetic variation, where not every cell in the body has the same DNA

growth factors

chemical signals that signal cell division

contact inhibition

stopping cell division in response to contact with other cells

cyclins

proteins that activate Cdks and are degraded at the end of mitosis

cyclin-dependent kinases (Cdks)

enzymes that phosphorylate other proteins and are stimulated by cyclins

checkpoints

occur after G1, late in the G2 phase, and between metaphase to anaphase, where cyclin binds to a cdk and activates cascade of biochemical signals to prepare the cell for the next phase of the cycle

heredity

transmission of genetic characteristic from parent to offspring

karyotype

chart of all the 46 chromosomes organized by size

homologous chromosomes

23 pairs, where one is inherited by each parent

sex chromosomes

determine an individual’s sex

autosomes

non-sex chromosomes

diploid

cell with 23 pairs of chromosomes

haploid

sex cells that have 23 unpaired chromosomes

germ cells

sperm and egg cells

somatic cells

body cells

locus

position of a gene on a chromosome

alleles

alternative variations of the same trait

dominant

allele variation that is usually expressed phenotypically

recessive

allele variation that is often not expressed in the present of the dominant allele, is not shown phenotypically

homozygous

an individual has the same allele on both homologous chromosomes

heterozygous

individual has different alleles on the homologous chromosomes

genotype

all of an individuals genetic information and allele types

phenotype

the proteins the individual is able to produce and express

carrier

and individual that possesses the recessive allele but does not express it

punnett square

method for finding inheritance probabilities

multiple alleles

when a gene has more than two alleles

gene pool

collective genetic makeup of the population

codominant

when both alleles are equally dominant resulting in both being expressed

incomplete dominance

two different alleles present and the phenotype is an intermediate of the two traits

polygenic inheritance

2+ genes contribute to one trait

pleiotropy

one gene produces multiple traits

sex-linked traits

carried by the X or Y chromosomes and tend to be inherited by one sex over the other, usually dependent on the X chromosome because it is larger

gene expression

gene being turned on and effects the individual

incomplete penetrance

when a dominant allele is silenced and is not expressed by those who carry it

epigenetic effects

activating or silencing genes without the change in base sequence, thus changing gene expression

epigenetic inheritance

can pass on changed in gene expression to offspring without changes in base sequence of gene