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yr.11 Human Biology > DNA, mitosis, stem cells > Flashcards

DNA, mitosis, stem cells Flashcards

(51 cards)

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1
Q

mtDNA

A

Mitochondrial DNA, 5-10 mtDNA molecules in mitochondria
1% of total DNA
Found in Mitochondria
forms circular DNA molecule
37 genes, 24 for making tRNA, 13 for making enzymes necessary for cellular respiration

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2
Q

DNA structure

A 
Is a polymer (molecule of many repeating units)
made of nucleotides
in form of strands
Two strands twist into double helix
2-3m long 1 millionth of m thick 
Order of bases determines genetic code.
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3
Q

nucleotide

A

Small repeating units
composed of: deoxirybose, phosphate group, nitrogenous base
Sugar molecule of one nucleotide bonds phosphate group of another one
two strands join by specific nitrogenous bases being attracted to one another by weak hydrogen bonds
Up to 2 million codes
average chromosome is made of 140 million base pairs

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4
Q

Types of nitrogenous bases

A 
adenine
Thymine 
cytosol
guanine
Uracil (RNA)
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5
Q

Chromosomes

A

super-coiled structures
Made when cells divide
large enough to see with light microscope
46 in each human cell
Each chromosome is made up of sections of DNA that code for particular proteins
each section called a gene.

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6
Q

Chromatin

A

DNA when cell isn’t splitting

Forms tangled network in nucleus

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7
Q

Histone

A

Protein in which DNA wraps around to form nucleosome

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8
Q

RNA

A

Ribonucleic Acid
Sugar molecule is Ribose not Deoxyribose, ribose has 1 more oxygen atom
RNA is single stranded
Has uracil no thymine
Strand able to fold on itself, forming hydrogen bonds between complementary bases

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9
Q

types of RNA

A

mRNA
rRNA
tRNA

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10
Q

mRNA

A

messenger RNA
Made in nucleus and takes genetic code into cytoplasm allowing genetic code into cytoplasm allowing genetic code to be ‘read’ by ribosomes

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11
Q

rRNA

A

Ribosomal RNA
60% of ribosome mass, other is protein
Ensures correct alignment of mRNA, tRNA and ribosome
also has enzymatic bonds between amino acids

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12
Q

tRNA

A

Transfer RNA
contains 70-90 nucleotides
Each tRNA is able to carry specific amino acid, therefore plays vital role in protein synthesis

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13
Q

start codon

A

AUG

Methionine

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14
Q

Stop codon

A

UAG

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15
Q

Transcription

A

process by which genetic instructions are copied from DNA to RNA
Transcription triggered by chemical messengers entering nucleus from cytosol and bind to relevant genes on DNA
Helicase enzyme seperates strands, usually 17 bases at time
RNA Polymerase then copies on one strand to create a strand of mRNA wt identical information as parent strand.
Often many polymerase follow first to make many copies at once

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16
Q

template strand

A

Strand that is copied

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17
Q

coding strand

A

Other strand

bases on strand will be identical to mRNA (except for uracil and thymine)

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18
Q

Translation

A

production of protein using info coded in mRNA molecule
In cytosol, ribosome attaches to one end of mRNA at start codon
ribosome then moves along mRNA 3 bases at a time
As ribosome reads codons on mRNA, tRNA with complementary bases join to mRNA
amino acids carried by tRNA are joined so protein is assembled wt amino acids in correct sequence

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19
Q

Gene expression

A

process of copying info from DNA onto mRNA, then translating the message into a series of amino acids to form protein
Cell is producing mRNA based on the cell’s purpose.
cell can produce up to 150 000 proteins per second
Genes used are ‘switched on’
genes not used are ‘switched off’

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20
Q

Factors affecting gene expression

A 
age of cell
Time of day
signals from other cells
Environment of the cells 
whether or not cell is dividing
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21
Q

Lipid and carbohydrate synthesis

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A

require no genes, however require enzymes
Enzymes are proteins
thus indirectly genes control synthesis of lipids and carbohydrates

22
Q

Epigenetic

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A

inheritance of factors that make genes more or less likely to be expressed
Changes in gene expression resulting from mechanisms other than changes in the genes

23
Q

genome

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A

Hereditary info coded in DNA

24
Q

Epigenome

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A

Sum of all factors determining where, when and which genes are expressed
therefore controls what proteins are synthesised
Epigenetic factors tell types of cells how to behave
Epigenome can change due to exposure to environment stimuli. These don’t change DNA but interfere transcription and translation

25
chromatin
For DNA to fit in nucleus, must be tightly coiled when cell not dividing DNA forms tangled network DNA and histones referred to as chromatin Gene expression may change if way DNA is wrapped around Histone
26
Types of gene expression based on histone
change of amino acids in histone Acetylation DNA methylation Histone Methylation
27
Change in amino acids in Histone
histone shape will change Modified shape is copied when no new molecules are formed ensures stem cells changed into specific cells remains that specific cell
28
Acetylation
addition of acetyl group to histone protein Reduces attraction of DNA and histone, relaxing structure of chromatin promotes transcription by allowing RNA polymerase access acetylation enhances gene expression
29
DNA methylation
Occurs by adding methyl group to DNA or Histone occurs where cytosine is adjacent wt guanine, known as CpG sites (cytosine-phosphorus-guanine) Methylation prohibits gene expression by restricting access to RNA polymerase
30
Histone methylation
Increase/decrease transcription of genes. Depending on where methyl group attaches and how many attach if methylation causes chromatin to relax, transcription increases
31
need for cell reproduction
Cells don’t grow, therefore more cells needed new cells needed to replace old, dead, damaged cells More wear and tear on cell, the shorter the life span
32
phases of cell cycle
``` G1 S G2 M G0 ```
33
G1 phase
Cell produces new proteins, grows and carries out its normal tasks phases finishes when DNA begins duplication
34
S phase
Synthesis phase | DNA molecules in nucleus form exact copies of each other
35
G2 phase
Second growth phase
36
M phase
Mitotic phase | Cell divides into two daughter cells
37
G0 phase
When cells leave the cell cycle and stop dividing
38
mitosis
Cell division division of nucleus Ensures each body cell receives exact same hereditary material (DNA) as parent cell process is continuous, doesn’t occur in steps
39
Stages of mitosis
Prophase Metaphase Anaphase Telophase
40
Interphase
period between cell divisions | Goes through G1, S and G2 phases
41
prophase
Two pairs of centrioles and opposite poles are visible, microtubules begin to radiate from them nucleolus disappears and nuclear membrane begins to breakdown Chromatin threads of DNA become tightly packed into chromosomes coiling of DNA makes it easier to distribute DNA to daughter cells
42
Metaphase
chromatid pairs line up on the equator of the spindle | Centromere attaches to a spindle fibre
43
Anaphase
Each pair of chromatids separates at the centromere | chromosomes are pulled towards opposite poles of cell
44
Telophase
Two sets of chromosomes form tight groups at each pole nuclear membrane forms around each group, nucleolus appears in each new nucleus Spindle fibre disappear chromosomes gradually uncoils to become chromatid
45
Cytogenesis
division of cytoplasm during telophase Furrow develops between two nuclei, gradually deepens until it cuts cytoplasm into two parts, each with own nucleus This along with mitosis results in 2 daughter cells
46
differentiation
Process by which cells become specialised during mitosis, different genes become activated, making stem cells into specialised cells. Specialised cells can divide therefore replaced by other means when stem cells undergo mitosis, daughter cells might be stem cell (stem cell proliferation) or differentiate
47
Stem cells
cells that undergo differentiation Not specialised for any role capable of repeated division by mitosis Potential to develop into any cell type means can provide unlimited source of cells for repair
48
stem cell types
Totipotent stem cells pluripotent stem cells Multipotent stem cells
49
totipotent stem cells
Potential to create any type of cell necessary for embryonic development
50
pluripotent stem cells
Can give rise to any of the cells in the body | embryonic stem cells are pluripotent
51
Multipotent stem cells
potential to form a number of different types of cells | Eg. Blood stem cell makes red, white and platelets

yr.11 Human Biology (10 decks)

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