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biology > DNA - protein synthesis - cell division - stem cells > Flashcards

DNA - protein synthesis - cell division - stem cells Flashcards

1
Q

dna function

A

control cell activity

codes for proteins

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2
Q

where is dna found

A

eukaryotes: the nucleus
prokaryotes: the cytoplasm (plasmid DNA, nucleoid)

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3
Q

nucleic acid

A

polymers of nucleotides

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4
Q

nucleotide

A

monomer of nucleic acids

pentode sugar deoxyribose, a phosphate group, and a nitrogenous base

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5
Q

bases

A 
5 types
G
C
A
T - only in DNA
U - only in RNA
(G-C, A-T/U)
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6
Q

triplet code

A

3 bases code for 1 amino acid

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7
Q

gene

A

a short section of DNA that codes for a protein

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8
Q

RNA

A 
another nucleic acid
different to DNA:
- shorter
- single stranded
- found outside the nucleus
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9
Q

why can’t genes leave nucleus

A

molecule is too big to leave the nucleo pores

so it’s copied and the copy goes to the ribosome where proteins are assembled

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10
Q

steps in protein synthesis

A
  1. Transcription - copy gene

2. Translation - ‘translate’ mRNA code into amino acids

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11
Q

transcription

A

in the nucleus

  • gene is UNZIPPED temporarily
  • mRNA reads and PAIRS complementary bases (U not T) of each nucleotide of the template strand (DNA)
  • mRNA can LEAVE the nucleus through the nucleo pores - short, single stranded
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12
Q

translation

A

on ribosomes
3 nucleotides > 1 amino acid
- mRNA leaves nucleus and ATTACHES to ribosome in the cytoplasm
- tRNA brings a SPECIFIC AMINO ACID according to the triplet code on the mRNA
- base pairs on tRNA are complementary to mRNA so tRNA ATTACHES TO mRNA on ribosome
- a second specific amino acid is carried to the ribosome
- the second tRNA attaches to its complementary sequence on the mRNA
- a PEPTIDE BOND forms between 2 amino acids
- the first tRNA LEAVES
- a POLYPEPTIDE CHAIN grows on the ribosome as the message is read and more amino acids are carried

4 bases code for
20 amino acids which code for
all proteins

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13
Q

mRNA

A 
messenger RNA
carries instructions from DNA in the nucleus to the ribosome
made in nucleus
short
single stranded
contains U not T
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14
Q

tRNA

A

transfer RNA

carries amino acids to the ribosome

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15
Q

why do cells divide

A

growth, repair, replacement

- a type of asexual reproduction - makes genetically identical offspring

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16
Q

cell division

A
  • cell GROWS + number of organelles increases
  • DNA in chromosome REPLICATES
  • further growth and DNA is CHECKED for errors
  • MITOSIS - chromosomes move apart + 2 nuclei form
  • cytoplasm DIVIDES in two and the new cell membrane separates off to give 2 new identical cells
17
Q

DNA replication

A

DNA is copied before division to ensure cells contain the same genetic info

  • double helix UNZIPS to form 2 strands
  • new bases line up using COMPLEMENTARY base pairing (A-T, C-G)
  • 2 identical strands are made
18
Q

mitosis

A
  • prophase- spindle fibres extend
  • metaphase - chromosomes line up in the middle
  • anaphase - chromatids pulled apart to opposite poles
  • telophase - 2 nuclei form
19
Q

prophase

A

FIRST STAGE
Chromosomes become visible
nuclear membrane dissolves
spindle fibers extend

20
Q

metaphase

A

Chromosomes line up in the middle of the cell

21
Q

anaphase

A

chromosome separates as spindle fibers pull them apart to opposite poles

22
Q

telophase

A

FINAL STAGE
After the chromosome seperates, the cell seals off
2 nuclei form

23
Q

interphase

A

period of the cell cycle between cell divisions

24
Q

how many pairs of chromosomes humans have

A

23 pairs = 46 total

25
Q

diploid

A

contains two sets of chromosomes (1 from mum, 1 from dad)

26
Q

why mitosis

A

ensures each daughter cell is genetically identical to its parent cell (so each cell can carry out its specialised function)

27
Q

stem cells

A

cells that haven’t become specialised (undergone differentiation)
can turn into many different cell types

28
Q

types of stem cells

A

embryonic

adult

29
Q

embryonic stem cells

A

found in embryos (blastocyst)

can develop into almost any cell type

30
Q

adult stem cells

A

found in adult tissues (e.g. bone marrow)

can only become a few cell types (e.g. blood cells (red/white))

31
Q

uses of stem cells

A
  • repair - replace damaged or diseased cells
  • growth - make new cells
  • research - can help leukaemia, diabetes, alzheimer’s, cancers
32
Q

why dont all cells divide

A

some cells have such a unique adaptation and function (such as nerve cells) with complicated structure and pathways so division would disrupt this
- cells whose function is determined do no undergo mitosis

33
Q

why use your own stem cells

A

your body’s immune systems may attack the donor cells and REJECT them

biology (20 decks)

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