Unit 2: Section 2 - Genetics Flashcards
Which nitrogenous bases specific base pair to each other?
Adenine and Thymine (A-T)
Cytosine and Guanine (C-G)
What 3 main things is a nucleotide made up of?
- phosphate group
- deoxyribose sugar
- nitrogenous base (varies, either A T C or G)
How many hydrogen bonds between the base pairs?
2 A-T
3 C-G
Give 3 ways DNA is well adapted for it’s function
- helical shape, makes it compact
- strong covalently bonded sugar-phosphate backbone in a double helix to protect genetic material
- genetic information (organic bases) have paired structure which makes it much easier to copy itself (self replication)
How is DNA stored in eukaryotic cells?
- DNA in double helix
- wound around proteins called histones
- histones also help to support DNA
- DNA wound round histones is coiled up repeatedly
- this forms a single chromosome
How is DNA stored in prokaryotic cells?
- same DNA double helix
- forms circular chromosome
- this is then coiled
- then supercoiled (like a snake to fit in cell)
How many organic bases form an amino acid?
3
Which two areas of DNA in eukaryotic cells don’t code for amino acids?
- DNA sections called introns
- DNA regions with multiple repeats outside of genes e.g. CCTTCCTTCCTT
How does DNA affect our nature, development and phenotype?
- DNA codes for certain alleles which control charecteristics e.g. Eye colour
- DNA determines amino acid sequence
- determines proteins and enzymes formed
- enzymes control metabolic pathways
- metabolic pathways help determine nature, phenotype and development
How can mutation cause none functional enzyme?
- deletion, addition, repetition of organic base
- change in amino acid sequence
- produces new allele which codes for protein
- enzyme is protein, if allele is different a different enzyme is produced
- because of different amino acid sequence it may not fold up properly
- different tertiary structure, active site different shape, not complementary to substrate
- cannot form enzyme-substrate complex
What is a haploid and diploid cell?
Diploid: number of chromosomes in normal body cells, have 2 of each chromosome (2n) one from mum, one from dad
Haploid: number of chromosomes in gamete, only one of each chromosome (only half from mum ovum or only half from dad sperm) (n)
What is an allele?
Different forms of the same gene
How many devisions in meiosis?
2
What is the centre of the double-armed chromosomes called?
Centromere
What is the single strand in a double-armed chromosome called?
Chromatid
What are the ‘poles’ in cell replication called?
Centrioles
Why is it important for gametes to have half the number of chromosomes as normal body cells?
- so when fertilisation takes place, the embryo formed has the correct diploid number of chromosomes
- if they had the normal number, the diploid number, that would mean the embryo formed would have twice the number of chromosomes it needs
Explain what crossing over is and how it leads to genetic variation
- during meiosis 1 homologous pairs of chromosomes come together
- the chromatids twist around each other and bits swap over (alleles)
- chromatids now contain different combinations of alleles
- this means each of the four daughter cells will contain chromatids with different combinationsof alleles
Explain meiosis (6)
- DNA unravels and replicates
- DNA condenses to form double armed chromosomes
- chromosomes arrange themselves into homologous pairs
- these pairs seperate meiosis 1
- the pairs of sister chromatids then seperate in meiosis 2
- four HAPLOID genetically different cells are produced
- in exam draw diagrams (especially if stated)
Explain what independant segregation is
- chromosome pairs can split up in any way
- so daughter cells produced can contain any combination of maternal and paternal chromosomes with different alleles
What is the founder effect and how does it reduce genetic diversity?
- few organisms from population start new colony
- less alleles reduced gene pool
- inbreeding, higher incidence of genetic disease
- caused by migration, seperation, even religion
What is selective breeding?
- select few organisms with desired charecteristics to breed
- they pass on genetic information with desired allele
- offspring express desired characteristic
- reduced gene pool
