bio exam 4 chap 11-13

blending concept of inheritance

blending concept of inheritance

cross between plants with red flowers and plants with white flowers would yield only pink flowers

particulate theory of inheritance

based on the existence of minute particles (genes), allowed Mendel to propose law of segregation and law of independent assortment

true breeding

self fertilization produces offspring identical to parent

monohybrid cross

parent plants differ in one character

law of segregation

four hypothesis: alleles are genes found in alternate versions responsible for variation, organism inherits two alleles (one from each parent), if alleles differ one determines the organism’s appearance (phenotype), genes in a pair segregate during meiosis and each sperm or egg receives only one member of the pair

Punnett squares

visual representation used to calculate the expected results of simple genetic crosses

locus

physical location of a trait or gene on a chromosome

alleles

alternate versions of a gene

dominant allele

masks the expression of the recessive allele

homozygous

has two identical alleles

heterozygous

two different alleles at locus

dihybrid cross

cross between two individuals with two different observed traits, F2 generation 9:3:3:1 ratio

law of independent assortment

each pair of alleles separates independently of all other pairs during gamete formation, only applies to alleles of traits on different chromosomes

testcross

cross between an individual with dominant phenotype and individual with recessive phenotype to determine if the dominant individual is homozygous or heterozygous

autosome

any chromosome that is not a sex chromosome

carriers

no abnormality but can pass allele for recessively inherited genetic disorder

rule of multiplication

multiply probabilities of events that must occur together

ex: probability of rolling a 6 then rolling a 5 -→ 1/6 * 1/6= 1/36

rule of addition

add probabilities of events that can happen in different ways

ex: probability of rolling either a 5 or a 6 -→ 1/6 + 1/6=2/6 or 1/3

pedigree

graphical representation of inheritance patterns of a single trait in families

examples of autosomal recessive disorders

methemoglobinemia, cystic fibrosis, phenylketonuria

examples of autosomal dominant disorders

osteogenesis imperfecta, huntington disease, hereditary spherocytosis

multiple alleles

gene exists in several allelic forms within a population, ex: ABO blood group

codominance

both alleles of gene are expressed equally in heterozygote, ex: AB blood type

complete dominance

one allele is dominant over the other, dominant allele determines phenotype

incomplete dominance

when heterozygote has intermediate phenotype between that of either homozygote

pleiotropy

when a single mutant gene affects two or more distinct unrelated traits (one gene influences many characteristics) ex: hemoglobin because it affects the shape of the cell and the type of hemoglobin produced

polygenic inheritance

trait is governed by two or more sets of alleles (many genes influence one trait), ex: eye color, skin color

epistatic interaction

when one gene can override another

law of segregation in meiosis

separation of homologous chromosomes in anaphase I

law of independent assortment in meiosis

alternative orientation of chromosomes in metaphase I

linked genes

located close together on the same chromosomes, tend to be inherited together

genetic maps

shows orders of genes on chromosome, arrange genes into linkage groups representing individual chromosomes

XX

female

XY

male

sex linked genes

located on either of the sex chromosomes

X linked genes

passed from mother to son and mother to daughter or father to daughter ex: color blindness, Menkes syndrome, muscular dystrophy, adrenoleukodystrophy

Y linked genes

passed from father to son

hemizygous

male posses only one allele for gene on X chromosome

nucleotides

deoxyribose sugar, phosphorus group, nitrogenous base (A, T, C, G)

covalent/phosphodiester

bonds to link nitrogenous bases

two hydrogen bonds

adenine and thymine

three hydrogen bonds

cytosine and guanine

hydrogen

bonds between complementary nitrogenous bases

purine

adenine and guanine, double ring

pyrimidine

thymine and cytosine, single ring

semiconservative

two double helix molecules each with one parental and one new strand

origins of replication

where DNA replication begins, produces bubble, proceeds in bith directions, ends when products from bubbles merge with each other

DNA helicase

unzips double stranded DNA to single strands by breaking H bonds

single strand binding proteins

bind to single stranded DNA and prevents it from reforming double helix during replication

DNA primase

synthesizes short RNA primers

DNA polymerase

synthesizes DNA in leading and lagging strands, removes RNA primers, fills gaps with more DNA, proofreads newly made DNA

polymerases

place complementary nucleotides in fork

DNA ligase

covalently attaches adjacent Okazaki fragments in lagging strand

antiparallel (opposite)

orientation of DNA strands/phosphate sugar backbone

3’ end

hydroxyl group attached to deoxyribose

5’ end

phosphate group attached to deoxyribose

5’-3’

direction DNA replication occurs

continuous

replication on 3’-5’ template

discontinuous

replication on 5’-3’ template, short segments

3’ end

end DNA polymerase adds nucleotides to

leading strand

exposed so synthesis in 5’-3’ direction is easier, replication is continuous, requires formation of single primer

lagging strand

has to be opposite direction so DNA polymerase synthesizes new strand in short 5’-3’ segments with periodic starts and stops, joined by DNA ligase, requires formation of new primer at start of each Okazaki fragment

primer

short segment of RNA

primase (RNA polymerase)

links ribonucleotides that are complementary to DNA template into primer

repair enzymes

uses visible light to break covalent bonds between bases that occur because of exposure to UV light

telomeres

end of eukaryotic chromosomal DNA, protect genes from being eroded through multiple rounds of replication

telomerase

uses short molecule of RNA as template to extend 3' end of telomere, lengthens telomere

prokaryotic DNA replication

one specific origin of replication site

eukaryotic DNA replication

numerous origins of replication, replication fork, takes longer to replicate but multiple origins speeds it up, linear chromosomes that make DNA polymerase unable to replicate ends of chromosomes (composed of telomeres)

one gene one enzyme hypothesis

based on studies of inherited metabolic diseases

one gene one protein hypothesis

expands the relationship to proteins other than enzymes

one gene one polypeptide hypothesis

recognizes that some proteins are composed of multiple polypeptides DNA genotype is expressed as proteins

mRNA

takes message from DNA in nucleus to ribosomes in cytoplasm

tRNA

transfers amino acids to ribosomes, matches amino acids to corresponding mRNA codon

rRNA

makes up ribosomes where polypeptides are synthesized

transcription

from DNA nucleotide language to RNA nucleotide language, DNA to mRNA/tRNA/rRNA

translation

from nucleotide language to protein language, mRNA is read by ribosome and converted to sequence of amino acids in polypeptide

central dogma

process that dictates flow of information from DNA to RNA to protein

genetic code

allows for conversion of DNA/RNA chemical code to sequence of amino acids in protein

codon

three base sequence in mRNA during translation directs addition of particular amino acids into protein or directs termination of process

redundant

more than one codon for some amino acids

unambiguous

any codon for one amino acid doesn’t code for any other amino acid

RNA polymerase

moves along the template strand in 5’ direction, adds nucleotide only to 3’ end

promoter

defines start and direction of transcription, RNA polymerases attaches to it

initiation transcription

RNA polymerase binds to promoter, helix unwinds and transcription starts

elongation transcription

RNA nucleotides added to chain

termination

RNA polymerase reaches terminator sequence and detaches from template

exons

sequence of mRNA with protein coding regions

introns

internal, segment of mRNA with no protein coding regions

cap

added to 5’ end, single guanine nucleotide, protects RNA from cellular enzymes

poly A tail

added to 3’ end, tail of 50-250 adenines, protects RNA from cellular enzymes

RNA splicing

removal of introns and joining of exons to produce continuous coding sequence

initiation translation

brings together components needed to begin protein synthesis

elongation translation

addition of amino acids to polypeptide chain

termination translation

polypeptide is released

anticodon

group of 3 bases complementary and antiparallel to mRNA codon

ribosomal subunits

small and large, have binding sites for mRNA and 3 for tRNA

small ribosomal subunit

binds to mRNA, an initiator tRNA pairs with the mRNA start codon AUG

large ribosomal subunit

completes the ribosome, initiator tRNA occupies the P site, A site is ready for the next tRNA

E site

exit site