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Flashcards in Genetics Deck (60):
1

Chromosome

A DNA molecule + associated proteins

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Telomeres

Multiple repeats of the 6 nucleotide sequence found at the end of chromosomes

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Centromeres

Area of the chromosome that the kinetochore forms/microtubules of cell division attach to

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Kinetochore

Structure that is formed on the centromere for microtubule attachment

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Diploid

2 copies of each chromosome

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Haploid

Single copy of a chromosome

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Tetraploid

4 copies of a chromosome, typically found in the liver

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Homologs

The same type of chromosomes, but from different cell sources (i.e. mom and dad)

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Chromatin

Protein structure DNA is bound to

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Nucleosomes

8 histone proteins that DNA winds around

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Euchromatin

Type of interphase nuclear structure that is less tightly packed and present in more metabolically active cells

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Heterochromatin

Type of interphase nuclear structure that is densely packed and present in less metabolically active cells

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Chromatids

One chromosome while the homologs are bound for cell division

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P-arm of chromatid

Shorter arm of chromatid

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Q-arm of chromatid

Longer arm of chromatid

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Metacentric chromosomes

Arms of equal size (more or less)

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Acrocentric chromosomes

Very short p-arms

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Telocentric chromosomes

Essentially only q-arms

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Interphase

Cells prepare for division

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G1-phase

Cell synthesizes proteins for DNA synthesis, checks over existing DNA/presence of growth factor

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S-phase

DNA suplicated

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G2-Phase

DNA checked again, cell prepares for division, centrioles duplicated/centrosomes associated

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Mitosis

Dividing a diploid cell into another diploid cell

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Prophase

Chromosomes condense, centrioles separate, mitotic spindle forms (ends when nuclear envelope breaks down)

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Prometaphase

Chromosomes attach to mitotic spindles, become aligned on metaphase plate

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Metaphase

Chromosomes aligned on metaphase plate (ends when chromatids begin to separate)

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Anaphase

Chromosomes pulled towards spindle poles (ends when chromatids are maximally separated

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Telophase

Lamins are dephosphorylated, nuclear membrane reforms, chromosomes de-condense

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Cytokinesis

Contractile ring of the membrane draws in, dividing the cell in two

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Meiosis

Cells are reduced from diploid to haploid

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Interphase 1

Similar to mitotic interphase, but DNA content increases from 2d to 4d

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Prophase 1

Homologous chromosomes must find and pair with one another, 5 stages: Leptotene, Zygotene, Pachytene, Diplotene, Diakinesis

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Leptotene

Chromosomes condense into thin (lepto-) threads and pair

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Zygotene

Synaptonemal complex forms between homologs to help keep chromosomes aligned as they condense (also allows for cross-over: zygo=yoke)

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Pachytene

Chromosomes become shorter and wider (pachy=thick)

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Diplotene

Synaptonemal complex breaks down, chiasmata is formed between homologs

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Chiasmata

Where cross-overs occurred between homologs

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Diakinesis

Chromosomes complete condensation, nuclear envelop breaks down

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Metaphase 1

Tetravalent homologs are aligned at metaphase plate, homologs attach to opposite poles

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Anaphase 1

Chiasmata holding homologs are severed, homologs move to opposite poles, while sister chromatids move to the same pole

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Telophase 1

Nuclear envelop reforms, giving rise to 2 secondary gametes

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Interphase 2

No DNA synthesis, only checking of DNA

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Prophase 2

Chromosomes condense, centrioles separate, mitotic spindles form, nuclear envelope breaks down

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Metaphase 2

Chromosomes align on metaphase plate

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Anaphase 2

Chromatids split

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Telophase 2

lamina dephosphorylate, nuclear envelop reforms

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Crossover

interchange of chromatid segments via chasms occurs during meiosis I

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Chiasma

temporary junction that chromatids form to transfer DNA

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Linked genes

genes that are inherited together

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Spermatogenesis steps/names

Spermatogonia–1ºspermatocytes–(M1)–2º spermatocytes–(M2)–spermatids–(spermatogenesis)–sperm

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Oogenesis

Oogonia–1º oocytes–(M1)–2º oocyte–(ovulation)–dies or is fertilized (M2)

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Fertilization

Sperm/oocyte form a zygote

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Aneuploidy

Gain/lose a single chromosome, is most common type of abnormality

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Polyploidy

Multiple copies of the entire genome (not viable)

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Trisomy 21

  • aka Downs syndrome, extra 21
  • Characterisitc facial/hand features, mental retardation, congenital heart defects, developmental malformations

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Klinefelter syndrome

  • Only in males
  • 47 chromosomes – XXY
  • phenotypically male, but hypogonadism

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Turner Syndrome

  • Phenotypically female
  • Only 1 X
  • absense of ovaries, short stature, webbed neck, board chest, wide nipples

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Angelman Syndrome

  • Microdeletion on paternal 15
  • Mental retardation, hypotonia, obesoti, hypogonadism, cryptorchidism

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Cri-du-chat Syndrome

  • deletion of part of 5
  • Mircocephaly, mental retradation, congenital heart disease, cry sounds like a cat

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Trisomy X

  • XXX
  • phenotypically female
  • typically tall, low IQ, learning disabilities