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Genetics > Intro to medical genetics > Flashcards

Intro to medical genetics Flashcards

1
Q

Genome, DNA

A

an organisms total DNA content. DNA=contains the genetic information needed to specify all aspects of embryogenesis, development, growth, metabolism, and reproduction-what makes us functional

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2
Q

diploid

A

organism that carries two genome copies. 2n=46

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3
Q

haploid

A

any cell that has 1n=23. Germ cells or gametes carry a single copy of the genome

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4
Q

human genome contained w/in nucleus:

A

22 autosomes and 2 sex chromosomes, x and y. additionally, DNA is also contained in the mitochondria.

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5
Q

Genes

A

sequences of base pairs that encode info for proteins, found on chromosomes. Range from <100 to several million bps.

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6
Q

exon

A

coding sequence

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7
Q

intron

A

non-coding sequence b/w two exons . . . regulatory element

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8
Q

Regulatory elements

A

HRE-hormone responsive elements
Promoters-always at 5’ end of gene, followed by introns and exons.
Enhancers

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9
Q

General features of a chromosome: Centromere

A

Centromere:repetetive sequences. Primary constriction on a chromosome-sister chromatids are held together here and kinetochore is formed. Attaches to mitotic spindle so chromosomes properly aligned during mitosis and meiosis and required for proper segregation of chromosomes.

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10
Q

General features of a chromosome: Telomere

A

the end of each chromosome arm. human telomeres end with tandem copies of TTAGGG, which is required for the proper replication of chromosome ends. Specialized Repetetive seqs of DNA-ensure integrity of chromosome during cell division.

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11
Q

General features of a chromosome: p and q arm

A

p=”petite” or short arm, q= long arm

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12
Q

Locus

A

location in the genome of a gene or genetic marker

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13
Q

alleles

A

alternative forms of a gene or a genetic marker

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14
Q

heterozygous

A

2 diff alleles at a locus (a,b)

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15
Q

homozygous

A

2 identical alleles at a locus (a,a)

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16
Q

haplotype

A

series of alleles on a single chromosome-likelihood to inherit one or the other haplotype from a parent is 50%. All alleles present on a single chromosome are referred to as haplotype

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17
Q

germline

A

cells that develop into gametes

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18
Q

somatic cells

A

all cells that contribute to one’s body

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19
Q

autosomes

A

22 pairs of chromosomes that are alike in males and females.

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20
Q

sex chromosomes

A

2 X in females; X,Y in males

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21
Q

homologous chromosomes/homologues

A

members of a pair of chromosomes; carry matching genetic information-they have the same genes in the same sequence; but may have different alleles

22
Q

alleles

A

identical or slightly different forms of the same gene. alternate forms of genes, multiple varieties coding for similar proteins

23
Q

Phenotype

A

Gene expression:observable characteristics:
physical
biochemical
disease status

24
Q

Cell cycle: how many chromosomes does a cell have entering mitosis?

A

4n=92

25
Q

Cell cycle

A

G1: Growth phase, immediately after mitosis; each cell has 1 diploid copy of genome.
G0: Arrested, non-dividing phase, neurons, rbc’s; liver cells-but not permanent
S: Synthesis, DNA content has doubled; each cell now contains 2 copies of the diploid genome. 4n=92
G2: Growth, ribonucleic acids, proteins are produced and cell enlarges->dbl mass before mitosis.

26
Q

Interphase

A

G1, S, G2 phases together constitute interphase

27
Q

Mitosis

A

occurs during cell division of somatic cells.
Diploid cell generates identical diploid cell.
No recombination (normally)

28
Q

Stages of Mitosis: Prophase

A

initiates mitosis, condensation of chromosomes and formation of mitotic spindle. Centrosomes,microtubule organizing centers, form foci from which microtubules radiate.

29
Q

Stages of Mitosis: Prometaphase

A

nuclear memb breaks up; chromosomes disperse and attach via kinetochores to microtubules of mitotic spindle. Congression: chromes move towards mid-point b/w spindle poles.

30
Q

Stages of Mitosis: Metaphase

A

chromosomes reach max condensation; alligned at equatorial plane of cell.

31
Q

Stages of Mitosis: Anaphase

A

Chromes separate at centromere->sister chromatids become independent daughter chromosomes, moving to opposite poles of the cell.

32
Q

Stages of Mitosis: Telophase

A

Chromes decondense, nuclear membrane reforms around each daughter nuclei and gradually resumes it’s interphase appearance.

33
Q

Stages of Mitosis: Cytokinesis

A

Cytoplasm cleaves, completing the process of cell division-> 2 complete daughter cells containing all genetic info of original cell.

34
Q

Meiosis

A

Occurs during gamete formation; a diploid progenitor cell generates four haploid gametes; 1 round of DNA synthesis followed by 2 rounds of chromosome segregation and cell division. Recombination frequent; has 2 phases: meiosis I, II are two successive meiotic divisions.

35
Q

Recombination

A

Exchange of genetic material b/w homologous chromosomes. must be b/w paired chromosomes, any other exchange can lead to mutation

36
Q

Meiosis I

A

aka “reduction division”-chromosome # is halved (2n->n) through pairing of the homologues in prophase followed by segregation to diff cells at anaphase. Recombination/crossing over occurs here

37
Q

Meiosis II

A

1 chromatid from each chromosome passes to daughter cell.

38
Q

Prophase I

A

chromes begin to condense; homologues pair and crossing over occurs->recombinant chromes. Chromes continually condense and become shorter and thicker during all 5 phases of prophase I

39
Q

Prophase I: Leptotene

A

chromes (already replicated during preceding S phase) condense; closely aligned-> indistinguishable. Form pairs of chromosomes(bivalents) consisting of 4 chromatids(tetrads)

40
Q

Prophase I: Pachytene

A

crossing over b/w pairs of homologous chromes to form chiasmata-point holding together 2 bivalents/tetrads which is the location of crossovers.

41
Q

Chiasmata

A

actual location of crossovers. 2 homologues of each bivalent are held together at this point.

42
Q

Prophase I: Diplotene

A

homologous chromes start to separate but remain attached by chiasmata. After recombination; synaptonemal complex begins to break down.

43
Q

Prophase I: Diakinesis

A

homologous chromosomes continue to separate, the chiasmata move to the ends of the chromes. Chromes meet max condensation.—> by telophase I the 2 haploid sets of chromosomes have normally grouped at opposite poles and the cell divides into 2 haploid daughter cells and enters meiotic interphase and meiosis II soon follows. *No S phase b/w the 1st and 2nd meiotic divisions.

44
Q

Meiosis II

A

n=23 chromosomes from reduction division. The 2 daughter cells from meiosis I divide to form 4 haploid cells, each containing 23 chromosomes. Similar to mitosis

45
Q

Meiosis II: Prophase II

A

chromosomes begin to condense and nuclear membrane dissolves, spindle fibers form.

46
Q

Meiosis II: Metaphase II

A

spindle fibers attach to chromosomes and they line up in center of cell.

47
Q

Meiosis II: Anaphase II

A

Centromeres divide and sister chromatids move to opposite ends of cell as spindle fibers shorten

48
Q

Meiosis II: Telophase II

A

Chromosomes reach opposite ends, nuclear membrane forms–>cytokinesis

49
Q

Spermatogenesis

A

Takes place after puberty in testes. Spermatozoa are formed in the seminiferous tubules after sexual maturity.

50
Q

Oogenesis

A

Begins during prenatal development.
-Diplotene arrest-oogenesis is arrested, incomplete–> will be completed in puberty under hormonal stimulation; primary oocyte–> secondary oocyte.
Metaphase arrest-2nd arrest during puberty at metaphase; will only be completed if there is fertilization. *chromosome abns more common in aging mothers b/c cells are arrested longer in diplotene.

Genetics (12 decks)

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