Heredity Revision Flashcards
What is binary fission?
Binary fission: DNA replication (Each copy attaches to a separate part of the cell membrane (no chromosomes or spindles)), 2 sides of the cell begin to pull apart, a wall forms across the cell dividing it into 2, separates into 2 cells.
What is mitosis?
Mitosis:
- Interphase (cell growth, production of organelles. DNA replication. Produces proteins necessary for mitosis.)
- Prophase (Chromosomes condense and become visible. Each chromosome comprises 2 chromatids. Spindle fibres begin to form. Nuclear membrane begins to break down.)
- Metaphase (Chromosomes line up along equator)
- Anaphase (Spindle fibres attach to centromeres. Spindle fibres pull chromatids to opposite poles of the cell)
- Telophase (Chromatids group together. 2 New nuclear membranes form. Chromosomes unravel. Cytokinesis occurs)
What is meiosis?
Meiosis: A process where a single cell divides twice to produce four cells containing half the original amount of genetic information (gametes).
- Prophase 1 (Homologous chromosomes pair up)
- Metaphase 1 (Homologous chromosomes line up along equator)
- Anaphase 1 (Homologous chromosomes pulled to separate sides of cell. Chromosome and copy go to one side)
- Telophase 1 (2 haploid cells form)
- Prophase 2 (Spindle fibres form perpendicular to first set)
- Metaphase 2 (Chromosomes line up along equator. Perpendicular to first set)
- Anaphase 2 (Chromosomes split at centromere. Sister chromatids separate to opposite poles)
- Telophase 2 (4 haploid daughter cells form)
What is fertilisation?
Fertilisation: fusion of 2 gametes
List the places in a cell where DNA can be found:
Cell nucleus and mitochondria
Describe the process of Protein synthesis:
- Transcription:
o RNA polymerase makes DNA separate (template strand & coding strand)
o RNA polymerase makes a copy of the DNA (pre-mRNA) by nucleotides joining to the template strand
o DNA codes to stop
o Methyl cap (5’) and poly A (3’) tail added
o Introns are removed to leave exons only- mRNA (splicing)
o Methyl cap- signalling molecule for ribosome
o Poly A tail- protects molecule from damage - Translation:
o Ribosome joins to binding site of mRNA
o Ribosome moves along mRNA (reading codons)
o tRNA bring AAs to ribosome
o tRNA anticodon binds to mRNA codon
o AAs join together using energy from ATP
o tRNA detaches
o mRNA is read until it reaches a stop codon
List the function of proteins in the body:
They act as enzymes that catalyse chemical reactions, provide structural support, regulate the passage of substances across the cell membrane, protect against disease, and coordinate cell signalling pathways.
Describe examples where the environment can have an effect on the phenotypic expression of the organism:
Different food, different exercise, low/high temperature, acid soil, alkaline soil
Describe the different types of mutation that can occur during cell division:
- Substitution: A substitution mutation occurs when one nucleotide is replaced by another.
o If the substitution mutation ends up coding for: - The same AA = neutral mutation
- Different AA = missense mutation
- New stop codon = nonsense mutation
- Insertion: An (insertion) extra base is added into the sequence.
- Deletion: (deletion) a base is removed from the sequence
Describe the role of crossing over in creating variation within a population:
- During prophase, homologous chromosomes pair up (synapsis) to forms a tetrad (four chromatids)
- Protein strings align the strands together and sometimes form connections called chiasmata (singular: chiasma)
- At the chiasma exchange of genetic material between homologous (but not-sister) chromatids can occur (crossing over)
- Exchange of genes between maternal and paternal chromosomes creates new gene combinations ( variation)
Describe the role of random assortment of chromosomes in creating variation within a population:
- Homologous chromosomes separate independently of each other during meiosis (Metaphase 1) and therefore traits are passed on independently of each other (except for genes on the same chromosome- gene linkage)
- When chromosomes align along the equator in homologous pairs
- Whether the chromosome on the left in homologous pair 1 is from the mother or father has no bearing on whether the left chromosome in homologous pair 2 is from the mother or father
- All homologous pairs align randomly, and are not affected in any way by the combination of the other homologous pairs in the cell
- Creates a huge number of possible chromosome combinations in the gametes (variation)
Describe the role of sexual reproduction and fertilisation in creating variation within a population:
- Random fusion of 2 gametes. Gives rise to an individual with a combination of two individual’s genes
Outline the process of Gel electrophoresis:
- DNA is cut up using different restriction enzymes (creates segments of different lengths)
- Fluorescent dye is added to samples
- Samples are added to the wells in the gel at the negative electrode end (including samples of a known size which scientists use to estimate the size of the fragments)
- Electricity is run through the gel and the negatively charged DNA is attracted to the positive electrode (smallest fragments move the furthest)
- DNA is viewed under UV light which causes it to fluoresce
Describe how gel electrophoresis is used for DNA profiling:
- DNA identification
- Genetic fingerprinting
- Paternity tests
- Bloodlines of livestock
- Genetic screening for inherited diseases/identifying diseases
- Monitoring biodiversity- wild & breeding programmes
Describe the process of gene sequencing:
- Gene cut into small pieces and amplified (in bacteria)
- Free DNA bases, DNA polymerase, DNA primers, terminator bases (G- yellow, A- green, T- Red, C- blue) mixed
- Heat to 96oC, Denatures DNA
- Lowered to 50oC binding of primer to DNA
- 60oC DNA polymerase adds bases until terminator base
- Heated to 96oC to separate strands
- Process repeated to create lots of different length strands
- 25 cycles produces 2 500 000 000 000 strands
- The placement of the terminator bases is random therefore every strand is a different length
- Fragments separated by electrophoresis (10 hours)
- Laser fluoresces coloured tags as they reach the end of the gel, camera records colour , short ones first (single base)
- Colours converted to letters
