genes and inheritance Flashcards
1
Q
what are sources of variation
A
- random fertilisation: mother and father contribute half their DNA, each individual produces a number of sperm / ova, infinite number of possible combinations
- random assortment: of homologous chromosomes (same size, centromere location and staining pattern) during meiosis, each pair segregates independently of very other pair
- crossing over: of chromatids during meiosis (P1), matching regions on homologous chromosomes break off and reattach / reconnect to other chromosome (genetic recombination, mix from M / F)
- non-disjunction: failure of chromosomes to separate, monosomy (45) / trisomy (47), M1 / M2, aneuploidy
2
Q
what is the DNA / RNA structure
A
- DNA: double helix ‘ladder’ with sugar phosphate sides (deoxyribose) and base-pair ‘steps’
- nitrogenous bases: adenine pairs with thymine and cytosine pairs with guanine
- RNA: single strand, uracil in place of thymine, ribose
3
Q
how are genes expressed and what is a codon / anticodon
A
- DNA directs synthesis of proteins that in turn determines an organisms traits
- DNA - mRNA - amino acids - protein
- transcription and translation
- codon: sequence of 3 nucleotide bases that specify a particular amino acid
- anticodon: corresponding nucleotides of a codon
4
Q
what is transcription
A
- DNA unwinds / unzips (enzyme helicase)
- RNA primase add primer, starting point for polymerase
- RNA polymerase adds complimentary nucleotides
- mRNA detaches from DNA
- mRNA leaves nucleus via nuclear pores and attaches to ribosomes
- DNA double helix winds itself back up
5
Q
what is translation
A
- mRNA attaches to rRNA
- correct tRNA brings the correct anticodon and AA to the mRNA
- rRNA moves along the mRNA to read next codon for tRNA to bring
- next tRNA brings the correct anticodon and AA to mRNA triplet codon
- peptide bonds form between the AA
- tRNA detaches from mRNA to go find another AA
- repeat steps 2-6
- new protein chain is produced from AA and peptide bonds
6
Q
who was gregor mendel
A
- early geneticist
- breaded sweet peas
- traits of an inherited character can disappear / reappear / appear in different offspring and phenotypes are more likely to be represented than alternate forms
7
Q
what are the principles of inheritance (as said by gregor)
A
- alleles: do not blend, remain as discrete units of inheritance
- dominant: where alleles for a single gene are different, only one is expressed in the phenotype
- recessive: the other has no noticeable effect on appearance
8
Q
what is pure breeding / cross breeding
A
- P: same phenotype, produce progeny with same phenotype
- C: difference phenotype, gives light to dominant / recessive alleles
9
Q
what is a gene, allele and locus
A
- G: discrete hereditary factors that determine traits
- A: different forms of a gene, only one allele present in haploid gamete, usually 2
- L: position of a gene on a chromosome, occupied by alleles
10
Q
what is homozygous vs heterozygous
A
- homo: two alleles for one gene are the same
- hetero: two alleles for one gene are different
11
Q
what is genotype vs phenotype vs wild type
A
- G: genetic make up of an organism, allelic composition
- P: detectable characteristics / traits of an organism
- W: phenotype most commonly observed
12
Q
what is a monohybrid vs dihybrid cross
A
- M: organisms that are heterozygous for alleles of one gene
- D: organisms that are heterozygous for alleles of two genes
13
Q
what is a punnet square
A
- presents all possible allele combinations for a particular gene
14
Q
what are the two laws of genetics
A
- law of segregation: two alleles in a pair segregate (separate from each other) into different gametes during gamete formation
- law of independent assortment: alleles for each gene will segregate independently of each other during gamete formation
15
Q
what is incomplete and co-dominance
A
- in: expression of both alleles leads to an intermediate phenotype (red, pink, white)
- co: no single allele is dominant, each allele has its own effect (ABO blood types)
