Bio 101 Final Test

chromosome theory of inheritance

Mendelian genes have specific positions on chromosomes; chromosomes undergo segregation and independent assortment

color blindness; muscular dystrophy; hemophilia

What disorders come from the X chromosome

Barr body

in mammalian females, one of two X chromosomes in each cell is randomly deactivated and this is deactivated

Inactivation of X chromosome

involves modification of both DNA and histones; attaching methyl groups (-CH3) to each nucleotides; one of two inactivated

linked genes

genes located on the same chromosome that tend to be inherited together; deviate from Mendel’s laws

recombinant types

offspring with nonparental phenotypes (new combinations of traits)

Sturtevant

predicted the farther apart two genes are, the higher probability that crossover will occur therefore higher recombination frequency

Chromosomal basis of inheritance

genes have specific loci; chromosomes undergo segregation and independent assortment

linkage map

genetic map of a chromosome based on recombination frequencies; not representative of distance

map unit

distances between genes; one represents 1% recombination frequency

Turner Syndrome

Give an example of a monosomy disorder

Trisomy 21 and Klinefelter

Give two examples of trisomy disorders

Deletion, duplication, inversion, translocation

What are the 4 main mutations for chromosomes

Base composition of DNA varies between species; % of A&T and G&C bases are equal

Define Chargaff’s Rules

bacteriophages

virus that infects bacteria and is widely used in molecular genetics research

origins of replication

two DNA strands are separated which opens a replication “bubble”

replication fork

at end of each bubble, there’s a Y-shaped region; parental strands of DNA are being unwound

Helicases

enzymes that untwist the double helix at the replication forks

Single-strand binding proteins

bind to and stabilize single-stranded DNA

Topoisomerase

relieves strain caused by tight twisting ahead of replication fork by breaking, swiveling, and rejoining DNA strands

RNA primer

initial nucleotide strand when synthesizing new DNA strand; nucleic acid sequence composed of ribonucleotide

primase

enzyme that starts RNA chain with single RNA nucleotide and adds RNA nucleotides one at a time using parental DNA as template

DNA polymerase

catalyze elongation of new DNA by adding nucleotides to 3’ end of preexisting chain

sugar attached to base and to 3 phosphate groups

Each nucleotide added to a growing strand of DNA consists of:

dATP

base used to make DNA; deoxyribose ATP compared to ribose ATP; as monomer nucleotide joins DNA strand, loses two phosphate groups

Okazaki fragments

series of segments called from synthesizing lagging strands; Gaps joined by DNA ligase

trombone model

two DNA polymerase molecules reel in parental DNA and extrude newly made daughter DNA molecules

mismatch repair

other enzymes remove and replace incorrect nucleotides

nuclease enzyme

cuts out and replaces damaged stretches of DNA

telomeres

a special nucleotide sequence at the end of eukaryotes DNA; postpone shortening of DNA molecules;

telomerase

catalyzes the lengthening of telomeres in germ cells; not active in most human somatic cells but under study as target for cancer therapies

histones

responsible for first level of DNA packing in chromatin; amino acid of each extends outward from nucleosome

nucleosome

consists of DNA wound twice around a protein core of 8 histones

heterochromatin

During interphase, centromeres and other parts of chromosomes are highly condensed; condensed chromatin

euchromatin

Loosely packed, open, and uncoiled chromatin

nucleic acid hybridization

complementary base pairing of DNA; base pairing of one strand of nucleic acid to another

genetic engineering

direct manipulation of genes for practical purposes; nucleic acid hybridization forms foundation

DNA cloning

scientists prepare well-defined segments of DNA in identical copies to work directly with specific genes

plasmids

bacteria; small circular DNA molecules that replicate separately from the bacterial chromosome

recombinant DNA molecule

a result of researchers obtaining a plasmid and inserting DNA from another source (”foreign DNA”) into it using restriction enzymes

cloning vector

plasmid that carries cloned DNA

restriction enzymes

cut DNA molecules at restriction sites (specific DNA sequences)

restriction fragments

many cuts in a long DNA molecule resulting from a restriction enzyme

sticky ends

bond with complementary ends of other fragments; most useful restriction enzymes cleave DNA in staggered manner to produce these

gel electrophoresis

separates a mixture of nucleic acid fragments based on length to see the fragments produced by cutting DNA molecules with restriction enzymes

PCR

produces billions of copies of a specific target segment of DNA; 3 step cycle; provide specific DNA fragment to be cloned; used to amplify DNA from wide variety of sources;

PCR

tests used to detect presence of viruses such as HIV, SARX-Cov-2

DNA sequencing

complementary base pairing is exploited to determine the gene’s complete nucleotide sequence

CRISPR

uses Cas9 nuclease which cuts double-stranded DNA molecules as directed by a guide RNA that is complementary to the target gene

Gene expression

process by which DNA directs the synthesis of proteins transcription and translation

transcription

synthesis of RNA using information in DNA; Eukaryotic cells modify RNA after transcription, during RNA processing both ends of primary transcript are altered; enzymes in eukaryotic nucleus modify RNA processing before genetic messages dispatched to cytoplasm

DNA to protein

What is the goal of gene expression?

Translation

Translate RNA to protein using tRNA (transfer RNA); synthesis of polypeptide using information in mRNA; ribosomes

single stranded, uracil, build protein and moves to ribosomes

How is RNA different from DNA

central dogma

concept that cells are governed by cellular chain of command

cytoplasm, simultaneous, begin translation before transcription is finished

How is bacterial transcription/translation different from eukryotic?

transcription in nucleus, translation happens in cytoplasm on ER

How is eukaryotic transcription/translation different from bacterial?

primary transcript

initial RNA transcript from any gene prior to processing

RNA polymerase

pries DNA strands apart, carries out transcription, and joins together the complementary RNA nucleotides; can start chain without primer; Bacteria: 1; Eukaryotes >2;

promoter

DNA sequence where RNA polymerase attaches.; includes transcription start point and extends nucleotide pairs

terminator

sequence signaling the end of transcription in bacteria

transcription unit

stretch of DNA that is transcribed

Initiation, Elongation, Termination

3 stages of transcription and translation

hydrolysis of GTP

What is the energy for translation provided by?

TATA Box

decides where transcription begins; promotor DNA sequence that is crucial in forming the initiation complex in eukaryotes

polyadenylation signal sequence

RNA polymerase II transcribes this; RNA transcript released 10-35 nucleotides past this sequence

RNA splicing

portions of RNA molecule are removed and remaining portions reconnected; carried by spliceosomes

transcription initiation complex

completed assembly of transcription factors and RNA polymerase II bound to a promotor

Transcription Factors

mediate binding of RNA polymerase and initiation of transcription

RNA polymerase and transcription factors bind to promoter

Describe the first step in DNA transcription: initation

RNA polymerase moves along DNA strand from 3’ to 5’ and builds mRNA by matching free RNA

Describe the second step in DNA transcription: elongation

RNA polymerase reaches terminator and enzyme detaches from DNA

Describe the third step in DNA transcription: termination

mRNA, tRNA, and 2 ribosomal subunits

Describe the Initial stage of translation

recognition, unwinding, clearance

What are the 3 steps of initiating transcription with promoters?

contains both exons and introns as unprocessed transcript; introns spliced and includes

Explain pre-mRNA vs mRNA and the differnece

mRNA

Central Dogma; transport instructions within DNA out to cytoplasm, providing template that ribosomes read to assemble amino aicds

introns

noncoding regions/intervening sequences in RNA splicing

exons

other regions that are usually translated into amino acid sequences

alternative RNA splicing

genes give rise to 2+ different polypeptides, depending on which segments are used as exons

Spliceosomes

consist of proteins and small RNAs which catalyze the splicing process

triplet code

flow of information based on a series of nonoverlapping, three-nucleotide words; translated into chain of amino acids forming a polypeptide

codons

64; mRNA base triplets; read in 5’ to 3’ direction; specifies amino acid (1/20) to be placed at the corresponding position along a polypeptide; more than one may specify a particular amino acid

start codon

establishes the reading frame for mRNA

specialized RNA molecules; accelerate reactions by lowering activation energies by cleaving or joining RNA; within ribosomes, precursor to RNA processing

Ribozymes: What are they, what do they do, where do they occur

wobble

flexible pairing at third base of codon; allows some tRNAs to bind to more than one codon

anticodons

structures on tRNA to match the codon on mRNA

P

site that holds tRNA that carries the growing polypeptide chain

A

site that holds tRNA that carries next amino acid to be added to the chain

E

Exit site, where discharged tRNAs leave the ribosome

ribosomes binding to mRNA 5’, scanning to locate start codon, recruiting tRNA, assembling ribosome

What are the substeps of initiation for translation

tRNA delivers amino acid to A site, form peptide bond with growing chain, shift ribosome along mRNA by one codon

What are the substeps of elongation for translation

signal peptide

polypeptides destined to ER or secretion marked by these, which targets protein to ER

mark proteins for ER or secretion

What is the use of a signal peptide and signal-recognition peptide

Silent, Missense, Nonsense

What are the 3 types of single nucleotide-pair substitutions? All point mutations

nucleotide-pair substitution

(Point mutation) replaces one nucleotide and its partner with another pair of nucleotides

Silent mutations

mutation that has no effect on amino acid produced by codon

Missense mutations

mutation that changes one amino acid to another

Nonsense mutations

mutation that changes an amino codon into a stop codon resulting in shorter polypeptide

Frameshift Mutation

insertion or deletion of nucleotides alter the reading frame of the genetic message; all nucleotides will be improperly grouped, leading to nonfunctional protein