Bio Exam 2

Nucleotide Structure

Nucleotide Structure

Has a sugar molecule, either a ribose in RNA or deoxyribose in DNA attached to a phosphate group and a nitrogen containing base

Complementary Nucleotides

how bases match on opposite DNA strands through hydrogen bonding on their nitrogenous bases

Semi-Conservative DNA Replication

one strand from each parent is conserved and remains intact after replication has taken place

Helicase

unzips the two strands of DNA, breaks through H-bond that bolds the bases together

Primase

makes the primer that allows DNA polymerase to figure out where to go, is make of DNA

DNA ligase

helps glue together DNA fragments

DNA Polymerase

replicates DNA molecules to build new strand of DNA, cannot figure out where to start without primer

Topoisomerase

split DNA strands in order to relive stress, untangle replicating DNA

Leading Strand

DNA replication occurs continuously

Lagging Strand

DNA synthesis restarts many times as the helix unwinds which results in Okazaki fragments

Telomere

an enzyme that adds extensions to the template strand where RNA primer can bind , found at the end of each chromosome

Advantages of mRNA

• can make many mRNAs from one gene and can also make many proteins from one mRNA

• can change whether or not to make mRNA from DNA and how much

Transcription Unit

a region of DNA used as a template for type of mRNA

Promoter DNA

where the RNA polymerase and cofactors bind and transcriptions begins, recognized and bound by proteins

Terminator DNA

where transcription ends, has specific nucleotides that are recognized and bound by proteins

Difference between replication and translation

replication requires a primer to begin, translation does not

snRNA

• spliceosomes, proteins and small nuclear RNAs (snRNAs) removes introns

• snRNAs bind, recognize specific nucleotides at exon-intron junctions

tRNAs

• transfer RNAs, small stable RNAs w/ 70-80 nucleotides

• each type binds to a specific type of amino acid

• each type has 3 different nucleotides which is an anticodon

Start Codon

first codon of mRNA transcript translated by a ribsome

Stop Codon

a sequence of three nucleotides in DNA or mRNA that signals a halt to protein synthesis in the cell

Point Mutations

single base is added, deleted, or changed

Silent Mutations

base substitutions that result in no change of the amino acid or amino acid functionality when the altered mRNA is translated

Missense Mutation

a single base pair substitution alters the genetic code in a way that produces an amino acid that is different from the usual amino acid at that position; wrong amino acid

Nonsense Mutation

a sequence change gives rise to a stop codon rather than a codon specifying an amino acid

Frameshift Mutation

deletion or insertion of anything other than 3n (3, 6, 9, etc. ) nucleotides

Gene Expression in Prokaryotes

control of gene expression is mostly at the transcriptional level

Gene Expression in Eukaryotes

regulation of gene expression can occur at all stages in the process

Lac operon mRNA

makes proteins that help import the disaccharide lactose and break it down

DNA methylation

makes a chromosome more tightly packed because it makes DNA more attracted to itself and that limits gene expression

Histone acetylation

when amino groups are added to histone proteins, decreasing the attraction and making them unwind more, gene are more likely to be expressed more

Diploid Cell

2n, have pairs of homologous chromosomes

Haploid Cell

1n, have only one of each homologue, also gametes (eggs, sperm)

Sister chromatids

copies made by replication from one copy

Homologous chromosomes

not copies of each other, each inherited from a different haploid gamete

Gene

stretch of DNA that determines a certain trait, genes mutate and can take two or more alternative forms

Allele

one of the forms of genes

Meiosis I

meiotic spindle lines up homologous chromosomes next to each other, separates homologous chromosomes and sister chromatids stay together

Meiosis II

halves the amount of DNA, sister chromatids separate

Steps increasing genetic diversity

• Crossing over

• Random assortment of chromosomes

• Random fusion of gametes from different parents

Mendel's Law of Segregation

the two alleles in the parent "segregate" from each other during the formation of gametes

Independent Assortment

two alleles of two or more different genes get sorted into gametes independently of one another

Incomplete Dominance

a mixture of the alleles in the genotype is seen in the phenotype.

Co-dominance

both alleles in the genotype are seen in the phenotype.

Nondisjunction

errors in chromosome separation during meiosis

Autosomal

a specific gene that is not on a sex chromosome

Sex-linked

traits that are influenced by genes carried on the sex chromosome

Polygenic Traits

characteristic like height or skin color that is influenced by two or more genes, does not follow the pattern for Mendelian inheritance

Quantative phenotype

measurable phenotype that depends on the cumulative actions of many genes and the environment

Complex Epistasis

interactions of genes that are not alleles, the suppression of one such gene by the other, complex interactions between genes and traits

Chiasmata

where non-sister chromatids remain physically connected at points of exchange, can result in the exchange of alleles

Synapsis

happens during prophase I when homologous chromosomes become connected

Crossing Over

exchange of genetic material and produces new allele combinations on chromosomes

Nondisjunction

errors in chromosome separation during meiosis

Trisonomy

person has three copies of one of the chromosomes instead of two (47 instead of 46)

Monosomy

person is missing one chromosome in the pair (45 instead of 46)

Barr body

inactivated, condensed X chromosome found in female cells, essential to regulate the amount X-linked gene product being transcribed

SRY gene

located at the distal region of the Y chromosome, is necessary for determining male sex determination

Transcription

process whereby the DNA sequence in a gene is copied into mRNA; the process whereby a base sequence of messenger RNA is synthesized on a template of complementary DNA

Splicing

parts of pre-mRNA (introns) are chopped out and remaining pieces (exons) are stuck back together

Operons

sequence of DNA containing a cluster of genes under the control of a single promoter

Promoter

upstream sequence to which RNA polymerase binds

Operator

segment of DNA to which repressor protein binds