Exam One

Genetics

one or a few genes

Genomics

all genes (about 20,000)

whole genome sequence

Gregor Mendel

studied inheritance patterns in the 1800s

Human Genome Project

sequenced the 20,000 genes in 2003

Telomeres

end pieces of chromosomes

protect chromosome from shortening too fast

Centromeres

DNA sequences that are binding sites for kinetochore proteins

can be bound by microtubule spindles

Chromosomal Disorders

extra or missing chromosomes or extra or missing segments of chromosomes

cause 50% of miscarriages

karyotype used to diagnose

Karyotype

display of all chromosomes

number, morphology, content (banding pattern)

used to diagnose chromosomal disorders

Dosage Effect

having too much or too little of something

problem in chromosomal disorders

Monogenetic Diseases

one gene mutated

Autosomal

not sex-linked

Mendelian

Autosomal Recessive

not sick if heterozygous

50% of protein is enough

Autosomal Dominant

being heterozygous makes you sick/one copy enough to make you sick

Dominant Negative

mutant antagonizes the wild type and prevents it from working

Happloinsufficiency

50% of wild type protein is not enough

X-Linked Inheritance

gene on X-chromosome

sex-linked

males more affected because they only have one copy

Maternal Inheritance

mitochondrial genes passed down from mom because mitochondria come from the ones in the cytoplasm of the egg

Multifactorial Disease

two or more genes mutated/multigenic

most genetic diseases

complex inheritance pattern

Gene

unit of genetic information

Coding Gene

codes for a product

Noncoding Gene

does not code for a protein but is still important for cellular functioning

make ncRNAs and this is the final product

Locus

precise position inside or outside a gene

position on a chromosome

Nucleus

contains 46 chromosomes

Somatic Cells

diploid body cells

Gametes

haploid sex cells

Homologous Chromosomes

autosome pair from mom and dad

same genes with possibly different alleles

DNA Nucleotide Monomer

made of deoxyribose sugar, phosphate, and nitrogenous base

Purines

bulky nitrogenous base with two rings

adenine and guanine

Pyrimidines

nitrogenous base with one ring

thymine, cytosine, and uracil

Phosphodiester Bond

covalent bond that connects nucleotides

Backbone

made of alternating sugars and phosphates

bases point inward

5’ End

functional phosphate on the end on carbon 5

highly reactive with two very unstable negative charges

3’ End

functional hydroxyl on end on carbon 3

polar group that can undergo chemical reaction but is not as unstable

Antiparrallel

strands go in opposite directions in regards to the 5’ and 3’ ends

DNA Complementation

A-T with two hydrogen bonds

G-C with three hydrogen bonds

these fit together well because one is big and one is small

Chromosome

one long, linear double helix

Chromatin

DNA and proteins that are stuck to it

loose and throughout the nucleus if not dividing

compact and in distinct locations when dividing

Nucleosome

level of chromosome compaction

eight histones with 140 base pairs

beads on a string

Solenoids

level of chromosome compaction

beads even closer together

Mitochondrial Chromosome

similar to bacterial chromosomes

small, circular, many copies

37 genes involved in mitochondrial function that work with nuclear genes involved in making ATP

Endosymbiosis Theory

mitochondria (and chloroplasts) were free living bacteria until engulfed by eukaryotic cell, and the cell decided to keep it around

bacteria gets a safe environment and nutrients and eukaryotic cells gets ATP

mitochondria perhaps lost the genes that it did not need

Reference Genome

first genome sequenced

Single Unique Sequences

50% of genome

unknown function

interspersed between repetitive sequences

Repetitive Sequences

43.5% of genome

found throughout the genome hundreds or thousands of times

SINE

short repetitive sequences

LINE

long repetitive sequences

Transposable Elements

genes that can jump to a new location or to a new chromosome

can also make a copy that jumps

can cause disease by insertion inactivation

Insertion Inactivation

interruption of the protein from transposable element inserting itself into a gene

Aberrant Recombination

repetitive sequences are used to line up homologues for recombination

cell can make a mistake and line up the wrong sequences leading to duplication and deletion during recombination

Mitosis

division of somatic cells

one diploid cell to two diploid cells (clones)

Meiosis

division to make gametes

one diploid cell to four haploid cells

Interpahse

the majority of the cell cycle

the cell is doing what cells go

includes gap/growth phases and S phase (the synthesis phase where DNA is copied)

M Phase

mitosis and cytokinesis

Metaphase

phase of mitosis where chromosomes line up head to tail in one row

Anaphase

phase of mitosis where sister chromatids separate

Cytokinesis

cell (cytoplasm and cell membrane) splits

Why Metaphase is Good for Karyotyping

the chromosomes are condensed and easier to see at this phase

can determine different lengths, centromere locations, and sequences of G-banding

Homologous Recombination/Crossover

homologues swap fragments during meiosis-I

Meiosis-I

includes recombination

homologues separate

Meiosis-II

sister chromatids separate

Gametogenesis

making gametes using meiosis

Spermatogenesis

making sperm in males

starts at puberty and continues throughout life

Oogenesis

making eggs in females

starts in fetal development and eggs stay in prophase-I until ovulation during and after puberty

stay in meiosis-II until fertilization

Fertilization

sperm and egg meet in the fallopian tube

sperm that enters prevents other sperm from entering to prevent triploidy

egg completes meiosis-II

two pronuclei fuse

Nondisjunction

homologues or sister chromatids do not separate and go to the same cell

leads to trisomy and monosomy

Mosaic

result of nondisjunction in mitosis

cells differ from one another in the same organism

Down Syndrome

results from nondisjunction of chromosome 21/three copies of chromosome 21

older (>35) and younger (<13) mothers have an increased chance of nondisjunction and miscarriage

Structural Genes

make proteins

RNA

link between DNA and protein

had ribose sugar and uracil

single stranded

Exons

coding sequences that get translated into proteins

Introns

noncoding sequences that get spliced out

Promoter

promotes genes expression

at the 5’ untranslated region upstream of gene

where transcription factors and RNA polymerase bind

Start Codon

where translation starts

AUG

codes for methionine (met)

Stop Codon

where translation stops and the protein is releases

UAA, UAG, and UGA

Regulatory Elements

upstream and downstream elements that regulate expression of a gene

can be far away

enhancers, silencers, insulators

Poly-A Signal

3' untranslated region that adds the poly-A tail for stability

Related Genes

genes that make related proteins

usually in gene families

Clustered Genes

genes in similar locations on the same chromosome

can be gene families resulting from duplication then mutation

Psuedogenes/Dead Genes

maybe once made a protein but no longer do

may be similar to genes in a family

have promoters, introns, exons, etc.

some have make mRNA but introns are not spliced out perhaps due to mutations

Retrotranscription

mRNA without intron is reverse transcribed back into DNA than DNA jumps into chromosome

mRNA to cDNA

Transcription Initiation

the cell decides to transcribe

spatial and temporal regulation

transcription factors bind to promoter and regulatory elements

Transcription

DNA to RNA in the nucleus

RNA Polymerase-II

transcribes structural genes to make RNA in the 5’ to 3’ direction

reads DNA 3’ to 5’

Antisense Strand of DNA

template strand that RNA polymerase reads

Sense/Coding Strand of DNA

strand RNA polymerase does not read

matches the RNA

5’ Cap

added after transcription to the 5’ end for transport

Translation

occurs in the cytoplasm on ribosomes where mRNA makes protein

Ribosomal RNAs (rRNAs)

part of the ribosome

has a complementary sequence of the 5’ end of mRNA allowing it to line up correctly

Codon

three nucleotides for one amino acid

tRNA

has an anticodon that is complementary to mRNA and carries an amino acid

binds to the codon

Constitutive Genes

housekeeping genes that are not regulated

continuous expression

no TATA or CAT

Enhancers

DNA sequences for spatial and temporal regulation that promote transcription

far from gene

transcription factors bind to these

Silencers

DNA sequences for spatial and temporal regulation that stop transcription

far from gene

transcription factors bind to these

mRNA Splicing

remove introns and join exons

Alternative Splicing

one pre-mRNA can make many mature mRNAs and cells can choose what exons to include

Polyadenylation

AATAAA sequence

cleavage of 20 base pairs after poly-A tail is added for stability

Deamination

used in RNA editing where a nitrogen/amino group is removed

Epigenetics

turns genes on/off without changing DNA sequence using chromatin modifications

over or above the DNA sequence

DNA Methylation

methyl group added to cytosine

repressors bind and decrease expression

occurs during development

Histone Modifications

methylation, phosphorylation, and acetylation to histones to loosen or condense chromatin