Studied by 7 peoplePurines
Adenine and guanine, 2 fused rings
Pyrimidines
Thymine and Cytosine, 1 fused ring
5’ (5 prime)
Phosphate linked to 5th carbon in sugar
3’ (3 prime)
OH group linked to 3rd carbon in sugar
DNA replication step 2 (after unzipping)
Binding proteins attach to the exposed ends of each strand to prevent them from coming back together
What end is primer added to in DNA replication?
3’ end
What removes the RNA primers?
exonuclease
What is different about RNA’s sugar
Ribose, extra oxygen
What is different about the nucleotide bases of RNA?
Uracil instead of thymine
What does RNA polymerase bind to during transcription?
Promoter
What causes introns to form loops?
Small nuclear ribonucleic particles (snRPS)
What excises the introns?
Splicosomes
What sticks exons back together?
RNA ligase
Functions of proteins (6)
Development and repair
energy
hormones
enzymes
transport and storage
antibodies
What are prokaryotes’ version of histones?
Nucleoid-associated proteins
DNA methylation
A methyl group is added to the DNA which stops some genes from being expressed
Histone modification
Acetyl group is added, which loosens the DNA from being too tight around the histones, activates the gene
Order of the steps in mitosis / meiosis
Interphase
Prophase
Metaphase
Anaphase
Telophase
Cytokinesis
Mitosis interphase
The centrosomes and DNA duplicate
Mitosis Prophase
Centrosomes migrate to opposite poles, spindle fibres form
Mitosis metaphase
The spindle fibres align the sister chromatids along the equator of the cell
Mitosis Anaphase
The sister chromatids are separated, and brought to opposite poles
Mitosis telophase
A new nuclear membrane forms around the two groups of chromosomes
Mitosis cytokinesis
Cytoplasm is divided
Meiosis Interphase
DNA and centrosomes replicate
Meiosis prophase 1
Homologous pairs arrange themselves in tetrads, crossing over occurs, centrosomes migrate to either pole
Meiosis metaphase 1
The tetrads are arranged along the equator
Meiosis Anaphase 1
The HOMOLOGOUS CHROMOSOMES are separated and brought to opposite poles
Meiosis telophase 1
new nuclear membrane forms around groups of sister chromatids, then CYTOKINESIS
Meiosis prophase 2
nuclear membrane disintegrates
Meiosis metaphase 2
Sister chromatids are arranged along equator of cell perpendicular to how they were in meiosis 1
Meiosis Anaphase 2
Sister chromatids are separated and pulled to either pole
Meiosis telophase 2
new nuclear membrane forms, then CYTOKINESIS
Random segregation
It is random which cells get maternal vs. paternal chromosomes (alleles) during meiosis
Independent assortment
Its random whether the maternal goes on top of the paternal or the paternal goes on top of the maternal when they’re arranged in tetrads
Crossing over
When homologous chromosomes are arranged in tetrads, parts of them can form a chiasma, where sections of the chromosomes are exchanged
Recombitant chromatids
Due to crossing over they contain both maternal AND paternal alleles
What does SNP stand for?
Single nucleotide polymorphism
What is a SNP?
single nucleotide substitution
1% of population = ?
SNP
<1% of population = ?
Mutation
What must the environment ensure for fertilisation? (4)
Gametes can meet
Moisture
Food + shelter
Dispersal of young
Process of producing gametes
Gametogenesis
To sexually reproduce, organisms must be able to find a mate, therefore ? (2)
Must be a difference between species and between sexes
What environment uses external fertilisation
aquatic environments
How does the embryo receive nutrients in external fertilisation?
Direct diffusion between the water and the cell
Why are large numbers of gametes produced in external fertilisation?
Low chance of gametes meeting
How are chances of gametes meeting increased in external fertilisation? (3)
Cyclical reproductive behaviour
Synchronised gamete release
Mating behaviour
Drying out of gametes
dessication
What does more parental care result in?
Greater offspring survival chance, which means less offspring need to be produced at once
What do the leaves of bulbs store?
food
What does the terminal bud of a bulb do?
Produce a flower
What does the lateral bud of a bulb do?
Produce a new plant
What do rhizomes look like / where are they located?
Horizontal, underground
What does the terminal bud of a rhizome do?
Makes a flower
What does the lateral bud of a rhizome do?
Makes more rhizomes
What does a runner look like / where is it located?
Horizontal above ground
What do the terminal buds of a runner do once they touch the ground?
Make a new plant
What is unique about gymnosperms?
Their seeds are not housed in ovaries
What do the leaves of gymnosperms form?
Cones - can be male or female
What does the male cone of a gymnosperm produce?
Large amounts of pollen
What does a gymnosperm rely on for pollination?
Wind
Angiosperms
flowering plants
Function of petals
Advertise to pollinators
Function of sepals
Protect flower bud
Stamen structure
Filament tipped by anther x
What happens within the anther?
Sacs produce pollen via meiosis
What do pollen grains house?
Cells that develop into sperm
Carpal structure
Style with stigma
What is at the base of the carpal
The ovary
What is inside the ovary (flower)?
Ovules
What do ovules house?
Developing ova and supporting cells
Pistil
Single carpal or group of fused carpals
How are the male gametes of angiosperms produced?
Cells inside pollen sacs undergo mitosis
Pollination
Pollen moves from an anther to a stigma
What happens after pollen grain lands on the stigma?
A tube grows from the grain to an ovule. 2 male gametes go down the tube, one of them fertilises the ovum.
What does a fertilised ovule become?
Seed
What does the ovary become after fertilisation?
Fruit
Development of an angiosperm zygote stops until there are favourable environmental conditions, then ?
The seed germinates
Fungi vs plant
Cell wall but no chloroplasts or chlorophyll
Fungi structure
Hyphae
Mycelium
Sporangium
Hyphae
Long thin threads, make up fungi
Mycelium
Tangled web of hyphae
Sporangium
Capsule where spores are made
What division process makes spores?
Mitosis
Budding process
Outgrowth off parent organism, the parent nucleus divides and one of the nuclei move to the bud. The bud breaks off and becomes the new organism
Why would fungi choose to reproduce sexually?
Adverse environmental conditions
How do bacteria reproduce
Binary fission - cell forms DUMBBELL shape when doing this
Protists structure
unicellular or unicellular-colonial
How do protists reproduce?
Most by binary fission, some by budding
Ionising radiation energy
high
How can ionising radiation cause a mutation? (2)
If it hits DNA directly, it can break the covalent bonds between nucleotides causing the backbone to break. As DNA repair enzymes put the DNA back together, they may reassemble it in the wrong order
It can also knock electrons out of orbit of nearby molecules, causing them to ionise. They are now called FREE RADICALS. These free radicals can react with nearby DNA, and may prevent transcription or translation, resulting in loss of control of the cell cycle
Non-ionising radiation energy
Low, only UVC can do any damage (UVA and UVB stopped by ozone)
How can UV radiation cause a mutation? (1)
It can cause adjacent thymine or cytosine bases on the same DNA strand to link together to form a dimer. These dimers cause structural kinks in the DNA, preventing transcription and translation and resulting in loss of control of the cell cycle.
How can chemical mutagens cause a mutation? (general)
Can be put into DNA instead of a nitrogenous base (because they are chemically similar)
How do deanimating agents cause mutations?
They can change one base to another one
How do viruses cause mutations?
They insert their DNA into the host genome to reproduce. If they insert their DNA in the vicinity of a gene, this can cause a mutation.
How does a retrovirus turn its RNA into DNA?
Reverse transcriptase
What is radon?
A radioactive gas
What does radon release to cause mutations?
Ionising radiation
Note 
Flashcard (66)