Module 6.2 The Human Genome Flashcards

1
Q

Human Genome

features (6)

A
  • 3.05 billion bases
  • linear nuclear genome
  • circular mitochondrial genome
  • average gene size = 27,000 bp
  • 19,969 protein coding genes
  • 43,525 non coding genes (inconclusive)
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2
Q

histones

A
  • proteins high in lysine and arginine residues
  • act as spools that DNA winds around to create nucleosomes
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3
Q

nucleosome

A
  • structure = segment of DNA wound around eight histone proteins
  • fundamental subunit of chromatin
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4
Q

heterochromatin

A
  • densely packed chromatin found in the nucleus of eukaryotic cells
  • doesn’t enable DNA and RNA polymerases to access DNA which prevents DNA replication and transcription
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5
Q

euchromatin

A

lightly packed chromatin that allows the DNA to be replicated and transcribed in eukaryotic cells

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6
Q

chromatin

A

unraveled, condensed structure of DNA, packaged by histones in nucleus

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7
Q

chromosomes

features

A
  • thread like structures located inside nucleus of cells
  • single enormously long linear DNA molecule associated with proteins that fold and pack fine DNA thread into more compact structure
  • 22 pairs of autosomes and one pair of sex chromosomes (X & Y) = 46 chromosomes
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8
Q

homologous chromosomes

A
  • maternal and paternal chromosomes of a pair
  • sex chromosomes are non-homologous (maternal X, paternal Y)
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9
Q

linear chromosome

Specialized nucleotide sequences

3

A
  1. replication origin (many)
  2. centromere (one)
  3. telomere (two)
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10
Q

replication origin

A
  • location where duplication of DNA begins
  • many origins of replication to ensure that entire chromosome can be replicated rapidly
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11
Q

centromere

A
  • holds duplicated chromosomes together until ready to be moved apart
  • consists of large arrays of repetitive DNA
  • tightly packed heterochromatin region
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12
Q

telomere

A
  • at ends of chromosomes
  • repeated telomere DNA sequences + adjoining region = structures that mark end of chromosome and protect ends from being recognized by cell as broken DNA molecules
  • tightly packed heterechromatin region
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13
Q

haplotype

features (3)

A
  • aka haploid genotype
  • group of alleles in an organism that are inherited together from a single parent
  • can be all chromosomes from one parent or a minor part of a chromosome
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14
Q

gene

A
  • segment of DNA that contains the instructions making a particular protein or RNA
  • contains regulatory DNA sequences, exons, and introns
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15
Q

exon

A

protein-coding sequence in gene

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16
Q

intron

A
  • intervening non-coding sequences
  • removed by splicing to create mature RNA
17
Q

genes

regulatory sequences

A
  • responsible for ensuring that gene is expressed at proper level and time and at right location
  • spread out over tens of thousands of nucleotide sequences in humans
18
Q

LINE / SINE

A
  • Long / Short Interspersed Nuclear Element
  • retrotransposable elements, that invade new genomic sites using RNA intermediates
  • account for >34% of human genome
19
Q

transposons

types (4) + feature

A
  1. LINEs
  2. SINEs
  3. retroviral-like elements
  4. DNA-only transposon ‘fossils’

multiplied in genome by replicating themselves and inserting new copies in different positions

20
Q

simple sequence repeats

A

nucleotide sequences <14 base pairs that repeat for long stretches

21
Q

segmental duplications

A

large blocks of genome 1,000-200,000 bp long that are present at two or more locations in genome

22
Q

human genome

repeated sequences

3

A

54% of genome
1. transposons
2. simple sequence repeats
3. segmental duplications

23
Q

human genome

unique sequences

2

A
  1. genes (>50%)
  2. regulatory DNA
24
Q

Telomere to Telomere Consortium

A
  • reported complete sequence of female genome in 2022
  • published human Y chromosome from HG 002 genome that corrects multiple errors in HG 38 Y chromosome and added over 30 million bp of sequence to reference
  • potentially 0.3% errors
25
Q

Telomere to Telomere Consortium

CHM 13

A

special cell line almost completely homozygous for all chromosomes

26
Q

Human genome

Difficult sequencing areas

A
  • centromeres and telomeres (heterochromatin)
  • AT/GC rich regions
  • palindromic sequences
  • hairpin structures