(Exam 2) - Chapter 4: Genes and Genomes

gene

DNA segment that is expressed to yield a functional product

exon

coding sequence in genes

intron

noncoding sequence in genes

RNA contains (exons, introns, both):

both exons and introns

mRNA contains (exons, introns, both):

exons only

histone

gene that lacks introns

intron frequency increases with:

genome size and complexity

functional products encoded by introns

proteins and noncoding RNAs

alternative splicing

different proteins are encoded from the same gene by joining exons in different combinations

simple-sequence repeats

tandem arrays of short sequences (1 - 500) of nucleotides

quaternary structure

interactions between different polypeptide chains in proteins composed of more than one polypeptide

number of polypeptide chains in hemoglobin

four polypeptide chains

gene family

members of a group of related genes

2 ways gene families are transcribed

in different tissues

at different stages of development

prokaryotic DNA

single chromosomes, circular DNA

eukaryotic DNA

multiple chromosomes, linear DNA

chromatin

a complex of DNA and proteins

major proteins in chromatin

histones

H1

type of histone

H2A

type of histone

H2B

type of histone

H3

type of histone

H4

type of histone

nucleosome

basic structural unit of chromatin

nucleosome core particles

147 base pairs of DNA wrapped 1.67 turns around a histone core (sealed by, but doesn’t include H1)

chromatosome

H1 bound to DNA where it enters the core particle

number of histone molecules in one nucleosome core particle

8 (2 of each histone, not including H1)

total condensation of DNA with histones

fiftyfold

euchromatin during interphase

loosely condensed, distributed throughout the nucleus

heterochromatin during interphase

highly condensed, ~10% of all chromatin

heterochromatin functionality

transcriptionally inactive, highly repeated DNA sequences

centromere

DNA sequences to which proteins bind, forming a kinetochore

spindle microtubules bind to:

the kinetochore

telomere

sequence at the end of a chromosome, required for replication of linear DNA molecules

telomere structure

repeated sequences that forms a loop structure and ends with a 3’ overhang of single-stranded DNA

telomere function

stabilizes DNA and resists degradation; determines lifespan/reproductive capacity of cells

telomerase

synthesizes telomeres via reverse transcriptase