Genetics Exam 3

Centric fragment

A piece of chromosome containing a centromere

Acentric fragment

A chromosomal piece without a centromere

dicentric chromosome

A chromosome with two centromeres

Inversion

The replacement of a section of a chromosome in the opposite orientation

deletion

the loss or absence of one or more nucleotides from a chromosome

Translocation

a part of the translation process in which the mRNA is shifted one codon in relation to the ribosome.

reciprocal translocation

A chromosomal configuration in which the ends of two nonhomologous are broken off and become attached to the non-homologs

deletion loop

See image

pseudodominance

the phenomenon in which a recessive allele confers the phenotype when only one copy of the allele is present, as in hemizygous alleles or in deletion heterozygotes

Deletion mapping

a technique used to find out the mutation sites within a gene

genetic imbalance

unnatural ratio of gene expression

Haploinsufficiency

lethal phenotype due to expression of only a single wild type allele

pericentric inversion

A chromosomal inversion that includes the centromere within the inverted region

paracentric inversion

A chromosomal inversion that does not include the centromere in the inverted region

Suppression (of recombination)

The phenomenon where a mutation (suppressor) restores the wild-type phenotype to a different mutation. the suppressor mutation may be in the same gene as the original mutation (intragenic suppression) or may be in a different gene (intergenic suppression)

variegation

Patchiness; a type of position effect that results when particular loci are contiguous with heterochromatin

duplication

extra copies of a chromosomal region are formed

aneuploidy

the condition of a cell or of an organism that has addition or deletions of whole chromosomes

euploidy

the condition of a cell or organism that has one or more complete sets of chromosomes

polyploid

anything above diploid

tetraploid

organism with four homologous sets of chromosomes

triploidy

organism containing three homologous sets of chromosomes

monosomy

absence of one member of a chromosomal pair

disomy

normal state of chromosomes in a eukaryote cell

trisomy

chrosomal abnormality in which there is one more than the normal number of chromosomes in a cell

nullisomic

A diploid cell missing both copies wof the same chromosome

Down syndrome

Trisomy 21 (three chromosomes on chromosome 21)

nondisjunction

the failure of a pair of homologous chromosomes to separate properly during meiosis

mosaic

Individuals made up of two or more cell lines with different genotypes that originated in the same zygote

heterochromatin

Chromatin that remains tightly coiled ( and darkly staining) throughout the cell cycle (transcriptionally inactive)

Chromatin

The DNA-protein complex that composes the eukaryotic chromosome

ribose

a pentose sugar important as a component of ribonucleic acid

deoxyribose

a sugar that is a constituent of nucleic acids

phosphate

a salt of phosphoric acid

nitrogenous base

A molecule that contains nitrogen and has the chemical properties of a base

pentose sugar

5 carbon sugar

nucleotide

Basic structure of DNA and RNA that consists of a nitrogenous base, a sugar, and one or more phosphates

nucleoside

A sugar-base compound that is a nucleotide precursor. A 5-carbon sugar with a nitrogenous base attached

Purine

Double C and N rings, has Adenine and Guanine

Pyrimidine

Single C and N rings, has Thymine, and Cytosine, and Uracil

DNA base pairs

Adenine, guanine, cytosine, thymine

RNA base pairs

Adenine, guanine, cytosine, uracil

DNA

Deoxyribonucleic acid, heritable molecule

RNA

Ribonucleic Acid, single helix, shorter than DNA

dsDNA

double-stranded DNA

ssDNA

single strand DNA

sugar-phosphate backbone

Forms the structural framework of nucleic acids, including DNA and RNA, joins together nucleotides in a DNA sequence

phosphodiester bond

a chemical bond of the kind joining successive sugar molecules in a polynucleotide

Chargaff's ratios

Amount of A = T, amount of G=C

double helix

the normal structure of DNA consisting of two helices rotating about the same axis

antiparallele

parallel but orientated oppositely

complementarity

the correspondence of DNA bases in the double helix so that adenine in one strand is opposite thymine in the other strand and cytosine in one strand is opposite guanine in the other. relationship explains Chargaff's rule

histones

Arginine- and lysine- rich basic proteins making up a substantial portion of eukaryotic nucleoprotein

nucleosome

the basic structure of eukaryotic chromatin that is composed of approximately 165 base pairs of DNA wrapped around a histone structure that consists of two molecules each of H2a, H2b, H3, and H4

solenoid

contains six nucleosome per turn

2nm fiber

short region of DNA double helix

11nm fiber

1st level packaging (nucleosome) "beads- on- a- string" form of chromatin

30nm fiber

2nd level (solenoid)

240nm fiber

3rd level (chromosome scaffold)

700nm fiber

4th level condensed scaffold

1400nm fiber

metaphase chromosome

chromosome banding

Characteristic banding pattern in chemically stained chromosomes

euchromatin

Eukaryotic chromosomal regions that are diffuse during interphase and presumably are the regions that are actively transcribed. (transcriptionally active)

Facultative heterochromatin

can shift between transcriptionally active and inactive states

centromeres

constrictions in eukaryotic chromosomes on which the kinetochore lies. Also, the DNA sequence within the constriction that is responsible for binding the kinetochore

telomere

the ends of linear eukaryotic chromosomes

C-value

genome size

C-value paradox

Genome size does not correlate with complexity of organism

transposon

repetitive DNA sequences that have the capability to move (transpose) from one location to another in genome

junk DNA

Eukaryotic DNA that lacks genes and has no known purpose

semiconservative replication

the mode by which DNA replicates, where each strands acts as a template for a new double helix.

theta structure

an intermediate structure formed during the replication of a circular DNA molecule

replication fork

The point at which the two strands of DNA are separated to allow replication of each strand

replication bubble

an unwound open region of the DNA helix from where the replication of DNA occurs

origin of replication

a sequence of DNA at which replication is initiated on a chromosome, plasmid or virus

DNA polymerase 1

removes RNA primers and replaces with DNA

DNA polymerase 3

Builds leading strand and Okazaki fragments

Primer

In DNA replication, a length of DNA or RNA, which is base paired to a single- stranded DNA template, that provides a 3' end for the addition of another nucleotide

leading strand

Strand of DNA being replicated continuously towards the replication fork

lagging strand

The DNA strand that is replicated discontinuously away from the replication fork

continuous replication

uninterrupted DNA replication in the 5' to 3' direction that is moving in the same directions the replication fork

discontinuous replication

DNA replication in short 5' to 3' segments that are moving away from the replication fork

Okazaki Fragments

Segments of newly replicated DNA produced during discontinous DNA replication on the lagging strand a

RNA Primase

A RNA polymerase that creates the short RNA primer for initiation of okazaki fragment synthesis during DNA replication. (places RNA primers)

Proofreading

the DNA pol reads the newly added base before adding the next one, so a correction can be made

3’ to 5’ exonuclease activity

Removes mismatched base pairs (proofreading)

Ligase

Joins Okazaki fragments into continuous daughter strand

helicase

unzips DNA

Single- strand binding (ssb) protein

maintains ssDNA

initiator proteins

(dnaA) bind to origin and separate

topoisomerase

relaxes supercoiling

template strand

The DNA strand that serves as the DNA template for transcription, which will be complementary to the RNA sequence; also the DNA strand that is used by DNA polymerase in a DNA sequencing reaction.

Exonuclease

exo- external
nucl - nucleous/ nucleic acid
ase - enzyme

gene expression

The process of producing a functional gene product

central dogma

the original postulate that information can be transferred from DNA to RNA and then to protein, barring any transfer originating from the protein

transcription

the process whereby RNA is synthesized from DNA template

translation

the process of protein synthesis wherein the nucleotide sequence of the mRNA determines the amino acid sequence of the protein

initiation (transcription)

RNA polymerase (RNAP) binds to promoter, DNA strand unwind, RNA polymerase builds RNA

elongation (transcription)

RNAP moves downstream elongating RNA transcript from 5' to 3', DNA strand rewinds after RNAP passes

termination (transcription)

RNA transcript (mRNA) is released and polymerase detaches from DNA