Bio exam 3

DNA

Molecules of all genetic material

DNA nucleotides

Adenine(A), Guanine(G), Thymine(T), Cytosine(C)

Purines

Adenine, Guanine -fused carbon nitrogen rings

Pyrimidines

Thymine and Cytosine- Single Carbon- nitrogen rings

polynucleotide chain

DNA nucleotides joined to form a polynucleotide chain linked by phosphate group in an alternating pattern, forming a sugar phosphate backbone

Phosphodiester bond

the linkage in DNA between adjacent deoxyribose sugars of 4 subunits of DNA

DNA Model

• double helix

• 2 polynucleotide chains twisted around like a double-spiral structure.

• Antiparallel

• diff polarities

• base pairs fill the central space

Purines

Adenine and Guanine

Pyrimidines

Thymine and Cytosine

Semiconservative replication

Hydrogen bonds between 2 strands break, unwind, and the strands act as a template for synthesis of the new complementary strand. New double helix has 1 old strand, derived from the parental DNA, and one new strand

Conservative replication

2 strands of the original molecule serve as templates for 2 strands of the new DNA molecule, then rewind into all “old molecule

Dispersive Replication

neither parental strand is conserved and both chains of each replicated molecule contain old and new segments

DNA polymerase

adds a nucleotide to the 3’ end of an existing nucleotide chain. Goes in 5’—>3’ direction. there are 4 types dATP, dGTP, dCTP, dTTP

sliding DNA clamp 

Protein that encircles DNA and attaches to the rear of DNA polymerase. Tethers DNA polymerase to template strand and increases rate of DNA synthesis

DNA Helicase

unwinds the DNA strands, producing y shaped replication forks

Single stranded binding proteins(SSB)

They coat the exposed single stranded DNA segments, keeping them from pairing.

Topoisomerase

Cuts and rejoins DNA to prevent twisting in circular bacterial chromosomes

Primer

short chain of RNA, synthesized by enzyme primase

Leading strand

direction of DNA unwinding, leading strand template

Lagging strand

New DNA strand synthesized discontinuously, in the direction opposite DNA unwinding

DNA Polymerase III

Main polymerase 5’—>3’

DNA Polymerase I

forms lagging strand 5’—>3’

DNA Ligase

Binds Okazaki fragments together

primase

Synthesizes RNA Primer to initiate strand

Replication Bubbles

unwinding at an ori causing 2 replication forks to join together

Tolomeres

Ends of most eukaryotic chromosomes protected by a buffer of noncoding DNA, short repeating sequences 

Telomerase

stops shortening of telomeres by adding telomere repeats to chromosome ends.

Proofreading mechanism 

allows DNA polymerase to back up and remove mispaired nucleotides

Base-Excision repair

mechanism repair nonbulky damage by removing the erroneous base and replace with correct one.

Nucleotide-excision repair

repairs bulky distortions in DNA by removing segment of DNA

Mutation

Changes in DNA sequence that passed on in replicated copies

Dominant

only 1 copy for the trait to be expressed

Recessive

Need 2 copies for traits to be expressed

Homozygote

contains 2 of the same alleles for a trait(true breed)

heterozygote

contains 2 diff alleles for a trait(hybrid)

Genotype

genetic constitution of a trait(allele)

Phenotype

physical apperances

Gene

Inhibited factor that determines a characteristic

Alleles

different variations of a gene

How many pairs of chromosomes in humans

23

P Generation

Parent generation, the original cross

F1 Generation

first offspring

F2 Generation

result of crossing F1 generation

Monohybrid cross

cross between individuals heterozygous for the same pair of alleles

Dihybrid cross

cross between individuals heterizygotes for the pair of alleles for 2 genes

Test cross

individual of unknown genotype is crossed w/  an individual homozygous w/ recessive genotype

Mendels law of dominance

cross between parents w/ conflicting traits will result in the appearance of 1 trait(dominance) and the masking of the other(recessive) in the next generation.

Mendels law of segregation

During formation of gametes, the 2 alleles for a trait separate, so each gamete carries only 1 allele for the trait.

Mendels principle of independent assortment

Alleles for diff traits separate independently from one another, the inheritance of 1 trait does not influence the inheritance of another

Suttons Chromosome theory of inheritance

Genes found on locus of chromosome, Similar to patterns of chromosomal inheritance

Incomplete dominance

Genotype of the dominant allele does not completely mask the effects of the recessive allele, resulting in an intermediate/blended phenotype red+white=pink

Codominance

Neither allele is recessive or dominant both are expressed equal red + white= red& white

Multiple alleles

Gene having 3 or more alternative alleles, but keep in mind a gene can only have 2

Epistosis

Gene interaction where expression of one gene(epistatic) masks the effect of the other (hypostatic) resulting in a different phenotype

Polygenic inheritance

multiple genes contribute to the same trait resulting in continuous variation of the trait

Pleiotropy

Single gene influences multiple, seemingly unrelated phenotypes.

Histone

a positively charged protein that helps package and organize DNA into structural units within the nucleus od eukaryote cells.

nucleosome

A segment of DNA wrapped around a core of histone proteins, forming the basic unit of chromatin structure.

Chromosome

is a tightly coiled and condensed form of DNA and proteins that carries genetic information in the cell.

Missense mutation

is a type of point mutation in which one DNA base is changed, causing the substitution of one amino acid for another in the resulting protein.(base pair)

Silent Mutation

is a change in a DNA base that does not change the amino acid coded for in the resulting protein.(base pair)

frameshift mutations

nucleotides are inserted or deleted from the DNA sequence in numbers not divisible by three, which shifts the reading frame of the genetic code.

Duplication mutation

segment of chromosome replicated( chromosomal)

Deletion Mutation

Segment of chromosome deleted(Chromosomal)

Insertion mutation

An insertion mutation is a genetic change where one or more extra nucleotides are added into a DNA sequence.

Inversion mutation

occurs when a segment of DNA breaks off, flips around (inverts), and reattaches in the opposite direction within the chromosome

Translocation mutation

happens when a segment of DNA breaks off from one chromosome and attaches to a different chromosome