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Biology > ch6- from chromosomes to genes > Flashcards

ch6- from chromosomes to genes Flashcards

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1
Q

DNA

A
  • a molecule which carries heritable information from one generation to the next.
  • packed into units called chromosomes
  • the DNA is tightly wound around proteins called histones. (they are positive, stick to wall well)
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2
Q

nucleotides

A
  • repeated units formed on DNA
  • four types: thymine, guanine, cytosine, adenine.
  • A-T- with 2 hydrogen bonds
  • G-C- with 3 hydrogen bonds
  • makes them complementary
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2
Q

Covalent bonds

A
  • strong
  • join the phosphates and sugars while nitrogen-containing bases are joined by hydrogen bonds (weak)
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2
Q

nucleotide structure

A

alternating phosphates and deoxyribose sugars form the sides of the ladder, with the bases forming the rungs.

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3
Q

gene

A

a section of DNA which carries coded information for making a protein or an RNA molecule

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4
Q

alleles

A

different versions of a gene
- for some genes only 1 version exists so all individuals will be the same but other genes have multiple alleles and this results in differences between individuals

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5
Q

meiosis

A
  • the process of forming haploid cells
  • most haploid cells are gametes (egg and sperm cells)
  • replication of DNA, then 2 sets of cell division so that the daughter cell contains only one member of each homologous pair and one sex chromosome.
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6
Q

chromatids

A

single stranded chromosome that is copied to become two identical strands.

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7
Q

genome

A

-the genome of an organism is all of its DNA, both coding and non-coding, in a haploid cell.

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8
Q

proteome

A

all of the protein in a cell

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9
Q

genomics and proteomics together

A

result in the development of therapies for people based on their own particular genetics.

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10
Q

karyotype

A

a picture of the chromosomes of an organism where the chromosomes have been paired up and arranged in order of size.

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11
Q

autosomes

A

all of the chromosomes except the sex chromosomes which are X and Y in humans and most mammals.

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12
Q

sex chromosomes

A

carries the gene that determines the sex of the individual

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13
Q

eukaryotic chromosomes

A

-linear and consist of multiple chromosomes (humans have 46)
- organized with histone proteins
- enclosed within nucleus

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14
Q

prokaryotic chromosomes

A
  • single and circular
  • without histones which is attached to the inside of the plasma membrane.
  • contain one or more plasmids
15
Q

meiosis- prior to cell division

A

single stranded chromosomes are copied to become two identical strands (chromatids)

15
Q

meiosis- stages

A
  • prophase 1
    -synapsis
    -crossing over
  • metaphase 1
  • anaphase 1
  • telophase 1
  • prophase 11
  • metaphase 11
  • anaphase 11
  • telophase 11
16
Q

meiosis- prophase 1 (crossing over)

A
  • the two close chromatids wrap around each other.
  • contact point is called chiasmata
  • the chromosomes at the chiasmata can break and swap pieces in a process called crossing over.
  • increase in gamete variation
16
Q

meiosis- anaphase 1

A
  • spindles retract towards the poles of the cell causing the homologous pairs to separate to either side.
16
Q

meiosis- prophase 1 (synapsis)

A
  • ## DNA condenses and chromosomes appear
16
Q

meiosis- metaphase 1

A
  • breakdown of nuclear membrane is completed
  • spindle fibers attach to centromeres of the chromosomes
  • the homologous pairs move to the equator of the spindle which is fully formed
17
Q

meiosis- prophase 11

A
  • new spindle forms
  • DNA condenses, chromosomes appear (double stranded)
  • the 2 daughter cells are haploid
18
Q

meiosis- telophase 1

A
  • chromosomes unwind
  • spindle breaks down
  • nuclear membranes form around chromosomes
    -cytokinesis occurs (the division of the cytoplasm)
  • results in 2 haploid cells
19
Q

meiosis- metaphase 11

A
  • the chromosomes line up in single file across the equator of the cell
  • spindle is connected to the centromere of the chromosome
20
Q

meiosis- telophase 11

A
  • new nuclear membranes form around each bundle of cells
  • spindle breaks down
  • chromosomes unwind and disappear
  • new nucleoli form (RNA)
  • four separate cells
20
Q

meiosis- anaphase 11

A
  • spindle fibres contract and pull sister chromatids apart
21
Q

role of crossing over

A

Crossing over produces new combinations of alleles on each chromosome, increasing genetic variation among offspring.

22
Q

role of independent assortment

A
  • how one pair of chromosomes, and hence alleles, separates is independent of how a different pair of different chromosomes separate.
  • all combinations are possible
23
Q

when non-disjunction occurs

A

meiosis I- homologous chromosomes fail to separate, leading to gametes with either an extra chromosomes or missing a chromosomes

meiosis II- sister chromatids fail to separate, resulting in similar errors with chromosomes numbers in the gametes.

23
Q

non-disjunction

A
  • chromosomes fail to separate properly
  • results in cells with an abnormal number of chromosomes
  • an error in cell division
24
Q

chromosomal errors

A
  • duplication - one segment repeated during crossing over
  • deletion - chromosome way be lost during cell division
  • inversion - DNA is read backwards
  • translocation - attached to non-homologous chromosome

Biology (8 decks)

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