5070 Deck 3: genetics concepts

central dogma of molecular biology

DNA →(transcription) → RNA → (translation) → PROTEIN

nucleotides

building blocks of DNA, RNA

nucleic acids

nucleotides linked together through dehydration synthesis

structure of nucleotides are?

sugar

nitrogen containing base

1-3 phosphate groups

base pairing of neucleotides

ATU

GC

any pairing outside of normal base pairing must be what?

corrected

the human geneome is what?

complete set of DNA, contains all the instructions for creating and maintaining humans

how many chromosomes does the human genome have? what makes up that number?

46

22 autosomes, 1 sex chromosome

how big is the human genome

~3 billion base pairs

euchromatin

more relaxed, genes highly expressed

heterochromatin

more tightly packed, genes poorly expressed

what condenses tightly during cell division?

chromosomes

what are DNA packed with in nucleus? what is this called?

histones

nucleosomes

what does methylation of DNA and histones cause nucleosomes to do? what does this cause the genes to do

pack more tightly together

genes are not expressed

acetylation of histones results in what? what happens as a result?

loose packaging of nucleosomes

DNA and genes are expressed

specific genes are located on ???

specific chromosomes

what is the short arm of the chromosome called?

the p arm

what is the long arm of the chromosome called?

the q arm

22 of our chromosomes are called what?

autosomes

what is the 23rd pair of chromosomes called?

sex chromosomes

what does diploid mean?

presence of pair of human chromosomes

each of one pair of a chromosome is from who?

one from each parent

autosome pairs can be described as what?

what does this mean?

homologous

similar in length, gene position, centromere location

allele def

location and content of one gene’s DNA sequence

peptide definiton

one or more amino acids linked by chemical bonds

polypeptide definitions

linked amino acids form these

proteins are made from multiple what?

proteins

what codes the amino acid sequence of proteins?

genes

what do genes contain? how are they arranged?

a segment of DNA

in a linear manner along a chromosome

what does a gene code for?

a specific protein or segment of protein that has a specific characteristic or function

what is the promoter of a gene?

base-pair sequence that specifies where transcription begins

RNA coding sequence is what?

base-pair sequence that includes coding information for the polypeptide chain specified by the gene

terminator

sequence that specifies the end of the mRNA transcript

before mitosis, what happens to DNA?

what does this produce?

completely replicated

two daughter cells with identical genetic material

what does DNA polymerase do? x2 things

synthesis of DNA

proofreading and correcting errors

DNA replication is what?

what does this mean?

semiconservative

each new DNA molecule has one original ‘parent’ strand and one new ‘daughter’ strand

what strand of DNA is continuously replicated? going in what direction?

leading strand from 5’ to 3’

what strand is discontinuously replicated?

going in what direction?

laggin strand

from 3’ to 5’

what does helicase do?

unzips the DNA through catalyzation

why is there high fidelity of DNA synthesis?

DNA polymerase makes ~120,000 mistakes during each replication

errors are proofread

what do replication errors become when they aren’t corrected?

mutations

what does error correction during DNA replication?

DNA polymerase III

how long is the gap that the lagging strand has? and where is it?

why is this?

100 bases at 5’ end

removal of the terminal RNA primer

through progressive cell division, what does the ‘gap’ on the lagging strand start to do?

starts to eat into the chromosome

chromosome gets shorter and shorter, loses functionality

what do telomeres do? what are they?

act like a ‘cap’ on chromosomes

noncoding DNA & binding proteins at ends of linear chromosomes

what do telomeres do to the chromosomes?

maintain structural integrity of chromosomes

the length of the telomeres is inversely proportional to what?

the # of times the cell has divided

telomerase enzyme does what?

where is this only present?

maintains telomeric length by adding more tandem repeats to chromosomes

germ cells, stem cells, cancer cells

what does RNA form?

single-stranded molecules

mRNA is what?

messenger RNA, directs synthesis of proteins

rRNA is what?

ribosomal RNA, forms core of ribosomes

tRNA is what?

transfer RNA, adaptors in protein synthesis

what is the most abundant type of RNA in cells?

rRNA

what is transcription?

the process of making an RNA copy of a gene sequence

messenger RNA is what?

what does it do?

copy of DNA

leaves the cell nucleus and enters the cytoplasm where it directs the synthesis of the specific protein it encodes

mRNAs are translated into what?

proteins

what is a characteristic of transcription?

it is highly selective

why is transcription highly selective? x2 reasons

signals in DNA that instruct RNA polymerase what to do

has regulatory proteins that are selective

what are three steps of transcription?

initiation, elongation, termination

what does RNA polymerase lack?

proof-reading capability

the promoter element of RNA provides what? x2 things

directionality to RNA polymerase direction

which DNA strand is used as a template

genetic code is redundant because why?

there are many possibilites for combinations of codons, but only 20 amino acids they code for

how many stop codons are there?

3 stop codons

having multiple codons that can code for the same amino acid does what?

reduces the possibility of an incorrect amino acid being synthesized

what is an exon

expressed sequence, translated into a protein

what is an intron

an intervening sequence, removed during splicing, not found in mature mRNA

what is the order of RNA replication?

DNA → transcription → pre-mRNA → splicing → mRNA → translation → polypeptide

during mRNA translation, what occurs?

mRNA is used to direct synthesis of a specific protein

mRNA directs synthesis of proteins in cooperation with what type of RNA and other cellular component?

tRNA

ribosomes

what does tRNA do?

translates mRNA codons to amino acids

translator tRNA has what 2 things attached to it?

anticodon

amino acid

what does tRNA do?

carries amino acid to ribosome to lengthen the growing peptide chain

mRNA codon and tRNA anticodon recognize one another how?

with complementary base pairing

ribosomes are the site of what?

where translation occurs

what is released from the ribosome?

how does it know to do this?

a newly synthesized protein chain

stop codon is reached

what base does RNA not have?

thyamine

are post-translational modifications encoded in DNA?

why do we do these modifications?

no

essential for the proper functioning of the protein, could be critical for folding

why do proteins fold?

what are they aided by

to achieve functional form

aided by chaperones

allele

how many copies are inherited

variant of gene sequence

one from each parent

alleles have the capability of being heterozygous, this means what?

alleles are different at any given gene locus

alleles can be homozygous, this means what?

the 2 alleles are the same

dominant allele is what

allele is phenotypically expressed whether homozygous or heterozygous

recessive allele is what?

an allele expressed only when present in homozygous condition

what is a carrier?

is the phenotype expressed?

someone who has a heterozygous recessive allele

phenotype not expressed

wild-type allele

encodes for the phenotype most common in a particular population. THE “NORMAL”

mutant/variant allele

any form of an allele other than the wild type

locus

physical place on a chromosome where a particular gene is located

penetrance

the # of people in population who carry disease-causing alleles and express the disease phenotype

complete penetrance

all people with the allele display the disease phenotype

incomplete penetrance

some people with allele do not display the disease phenotype

expressivity

what is variable expressivity?

degree to which a genotype is expressed phenotypically in individuals

varying degrees of having yes or no disease

mutation

change in DNA sequence

what are some potential mutagens?

radiation

chemicals

viruses

what are 2 types of mutations at the single gene level?

frameshift mutation

point mutation

frameshift mutation is what?

what does this do at the protein level?

adding or removing 1+ bases changes the ‘reading frame’

alters primary structure of protein

what is a point mutation?

what can this cause?

single base substitution

may cause affected codon to signify abnormal amino acid

what are the 3 subtypes of point mutations?

missense

nonsense

silent

missense mutation

what can’t this turn into?

wrong amino acid is made

NOT a stop codon

sickle cell anemia is due to what type of mutation?

what is the change that occurs?

missense mutation

valine (val) for glutamic acid (glu)

nonsense mutation is what

premature stop codon is inserted