Lecture 15 - Chromosome structure and genome organization - part 2 Flashcards
A genome is
an organism’s complete set of genes
Generally, higher organisms (plants, animals) have _______ genomes
larger
The human genome has approximately how many base pairs?
3 x 10^9
Genomic data indicate that the apparent number of genes roughly parallels
the organism’s complexity
Only about _____% of the genome encodes proteins
1.2
A gene can be identified by its
homology to a previously described mRNA or protein sequence
A protein-coding gene may also be identified as a(n)
open reading frame (ORF)
A ORF is
a sequence without stop codons
ORFs exhibit the same codon-usage preferences as
other genes in the organism
Computer-based gene identification algorithms rely on
sequence alignments with expressed sequence tags (ESTs)
ESTs are
cDNAs that have been reverse-transcribed from mRNAs
The functions of many human genes have been identified through
sequence comparisons of protein families and domains
The human genome contains approximately the same number of ___________ genes as other eukaryotes
“housekeeping”
The human genome contains relatively more genes for ________ than other eukaryotes
vertebrate-specific activities (immune system, neuronal, hormonal signaling pathways)
Nearly ______% of genes have unknown functions
42
Genes with no known functions are called
orphan genes
A significant portion of the human genome is transcribed to
RNA
About 4000 genes have been identified for
tRNAs, rRNAs, and other small RNAs
10,000s of genes have been identified for
noncoding RNAs (ncRNAs)
Protein-coding genes almost never occur in
multiple copies
Repeated translation of a few mRNA transcripts provides
adequate amounts of most proteins
Eukaryotic genomes contain
repetitive DNA sequences
Telomeres are composed of
repeating DNA sequences
p arm
short arm structure of chromosome
q arm
long arm structure of chromosome
centromere
constricted point of the chromosome
Nearly identical sequences approximately 10 bp long are ____________ in clusters of >10^6 copies per haploid genome
tandemly repeated
Short tandem repeats (STRs) make up about what % of the human genome
3%
STRs appear to have arisen by
template slippage during DNA replication
STRs exhibit a high degree of
length polymorphism
STRs analysis is widely used for
DNA fingerprinting
Moderately repetitive sequences arise from
transposons
~______% of the human genome consists of three types of retrotransposons
42
Three types of retrotransposons
- Long interspersed nuclear elements (LINEs)
- Short interspersed nuclear elements (SINEs)
- Retrotransposons with long terminal repeats (LTSs)
