[205 TERMS] Biol 300 UNLV Exam 1

Phenotype

organism's physical appearance

Heterozygous

Individual carries two alleles for a trait

If mother is A and father is B what can the Child's type be?

All types possible

Dihybrid Cross ratio

9:3:3:1

Neomorphic Phenotype results

Wild type & Mutant

Deficiency & Mutant

Duplication & Mutant

All display same phenotype

Constitutively Active Allele

Hypermorphic, cannot be rescued by wt, can result from nonsense mutation, is dominant, NOT loss of function

Antimorphic

Dominant, prevents wildtype from exhibiting, can be rescued by adding more wt

Two pure-breed tailless hamsters crossed, progeny all tailless, conclude that...

line mutations on same gene

Second site mutation

Mutation at different site in same gene restores original function

Spontaneous Mutation

Incorporation of wrong bases in replication

C1' on Pentose

Nitrogenous Bases are connected to

Purines

Adenine and Guanine

Pyrimidines

cytosine, thymine, uracil

C2' on Pentose

-H for DNA, -OH for RNA

C3' on Pentose

-OH (connects to C5' of another)

C5' on Pentose

Phosphate (connect to C3' of another)

Nucleotides made up of

Nitrogenous Base, Pentose, Phosphate group

Phosphate Group

Negative charge

Backbone of DNA

Phosphate and sugar (hydrophilic, - charge, outside of strand)

Neutralized by positive ions or basic proteins, could around same helix axis

Polarity of DNA

5' to 3'

Stablizing forces of DNA w/I base pair

Hydrogen bonding between complementary bases

Stablizing forces of DNA between base pairs

Base stacking force

Base Stacking force

Tendency of hydrophobic bases to stack to avoid watery environment (contributes to double helix)

Trasition

Purine->Purine

Pyrimidine->Pyrimidine

Transversion

Purine

Anneal

Renature, come together (DNA can anneal with RNA), highly specific

Tm

Temperature when half of DNA helix is seperated

Tm increased by

DNA length, G/C content (3 hydrogen bonds instead of 2)

Inversion

180 Rotation of a DNA sequence

Overwound Z-Form DNA

Righthanded supercoil

Underwound Z-Form DNA

Lefthanded supercoil

Frameshift mutation

Insertion of deletion of non-multiple of 3

Polymorphisms

Existence of two or more alleles for DNA sequence, inside or outside genes

Newly generated can appear as low frequency mutation

If allele frequency >1% not detrimental

Common Features between bacteria and organelles

binary fission, no nucleus, circular chromosomes, NOT 80S ribosomes.

What can cause polymorphisms

Missense, Tandem Repeats, Transposons, Insertions, NOT RNA splicing

Linkage Maps

A map of the genes on a chromosome based on linkage analysis, shows genetic distance NOT physical

Genomic Sequencing

Fragment sequencing and assembly

Mitochondria replicate by

Binary fission

Mitochondria typically come from

Maternal cells not sperm

Mitochondria membrane

Double Bilayer

Mitochondria Diseases

Usually maternally inherited however not always, DNA in nucleus can affect mitochondria diseases.

Redundant Genes

Nonessential, multiple genes have same function, loss of function genes can be partially compensated for, may be in parallel pathways

Gene Clusters

May be pseudogenes, may have different biochemical properties, may be expressed in different tissues, may be expressed in different stages, NOT orthologs

Evolution of globin gene family characterized by

change in temporal expression patterns, mutations creating pseudogenes, gene clusters, duplication and divergence of genes

In eukaryotes, are introns or exons larger

Introns are much longer

Prokaryote genome size vs gene numbers

Linear

Eukaryotes genome size vs complexity

Not a good indicator (repeats)

As organism complexity increases

Repetitive sequences and gene families increase

Majority of repetitive sequences in genome come from

Transposons

Genetic Drift

Random change in frequency of genetic variant in population

Types of Repetitive DNA

Transposon, Satellites, Telomere Sequences, rRNA, tRNA

Housekeeping and Highly expressed genes found in

Euchromatin

Telomerase uses what as template

RNA

Formation of T-loop depends on

tandem repeats

Telomerase

ribonucleoprotein that extends telomeres

Telomere overhang

3' end

terminally differentiated cells

telomerase is turned off

Centromere DNA sequence

Does not determine function

Condensation levels of centromere

Unchanged through cell cycle

Centromere DNA

rich in tandem repeats

Acentric Fragment

a fragment of a chromosome from breakage. that lacks a centromere, lost at cell division

Facultative Heterochromatin

Can be converted into euchromatin, telomerase encoding genes found here, transcriptionally silenced, highly condensed during interphase, Molecularly distinct

Centromeres are made of what chromatin

constitutive heterochromatin

Acetylation of Histones

Neutralize positive charge

DNA hypersensitivity

loss of nucleosomes, can still be bound by proteins, often found in promoters of actively transcribed genes, less likely found in heterochromatin

Core histones expressed at 1:1:1:1 ratio because

Genes are in same cluster and share promoters

Replication independent nucleosome assembly

Enrichment of H3.3 variant, nucleosome repositioning, does not involve DNA syntehsis

Haplosufficiency

A single allele produces sufficient amount of protein so phenotype is produced

Haploinsufficient

Protein level from one gene is not enough for normal function, phenotype of Aa is in between AA or aa or equal to aa. if Aa=aa LOF is dominant

Epigenetics

Chromosome packing not mutation (histone modification, methylation, chromatin remodeling)

Muller's Morphs

amorph, hypomorph, hypermorph, neomorph, antimorph

Amorphic

Complete LOF, can be rescued by wt, recessive to wt

Hypomorphic

Partial LOF, can be rescued by wt, reccessive

Hypermorphic

Too much activity/expression, dominant to wt, wt worsens condition

Neomorphic

New function not observable in wt, dominated, cannot be rescued by wt

Complementation Test

If two or more mutations that cause same phenotype on same gene, phenotype displayed, if on different genes wt displayed

B-Form DNA

Right Handed most common

Z-Form DNA

Left handed, certain special sequences

A-Form DNA

Right Handed, dehydrated form

DNA bases

No charge -> hydrophobic

Buried in side

Rings of base pair -> same plane (Z-form 20 deg tilt)

Parallel to other pair

Perpendicular to helix axis

Complete turn of helix

10 base pairs, minor and major groove

Minor Groove

Facing you, shorter

Major Groove

Facing away

Nonsequence-specific interaction

Charged backbone and histones

Sequence Specific Interaction (Key and Lock)

Groove and transcription factors

Direct Readout

Protein interest with base pairs via different shape of groove surface

Indirect Readout

Interaction with sugar or phosphate whose precise position and orientation is influenced by the base pairs

Supercoil formed by

Disruption of low energy state (< or > 10 base pairs) leads to strain, relieved by supercoil

Introducing supercoil

Bending (circular chromosomes) Overwound/Underwound (as you unwind other end winds)

Overwound DNA

More turns per DNA, less bp per turn

Coils in opposite direction

Underwound DNA

Less turns per DNA, more bp per turn

Coils in same direction

Topoisomerase I

Cuts a single strand of DNA

Topoisomerase II

Cuts both strands, removes supercoil

Two catalytic activates of topoisomerase

Endonucleases (cuts) attacks internal bonds

Exonucleases (Nibble from ends outside)

Topoisomerase required for

Replication, transcription. and reverse transcription

Induced Mutations

Due to mutagens

Types of mutations

substitution, insertion, deletion

Types of Mutation by scale

Point mutation, insertion/deletion, chromosome rearragnement

Point Mutation

Single base pair change

chromosome rearrangement

Caused by breakage of DNA at two location, rejoining of wrong ends. Can be within or between chromosome