cell reproduction, mutations, inheritance Flashcards
3 types of reproduction
asexual - binary fission - mitosis sexual - meiosis
binary fission steps
- single cell 2. bidirectional replication of circular dna - chromosomes replicate - moves to opposite sides and cell grows 3. cell elongates - cleavage furrows form 4. cell splits - 2 identical daughter cells are formed each eith a copy of the genetic material
sexual vs asexual
sexual: - 2 parents - fusion or female and male cells - parents and offspring not identical - slower - variation asexual: - 1 parent - no gametes produced - parent and offspring identical - faster - no variation
vegetative propagation
plant asexual reproduction runners: side branch that grow along the surface, roots grow down developing new plants eg strawberriers tubers: provide energy and nutrients for regrowth eg potatoes, roots then tuber bulb: short stem with fleshy leaves, onion, onion then roots
variation and types
1.independent assortment of chromosomes in meiosis - separation of chromosome pairs at meiosis 2.random mating and fertilisation of gametes - punnet squares - possibly recombinations at fertilization 3.crossing over during meiosis - swap genes from 2 homologous chromosomes - can separate linked genes 4.mutations - changes in gene or chromosome
IPMATC
I - dna replication occurs, chromosomes not visible P - nuclear membrane disappears - dna shortens into chromosomes - cell has 2 chromosomes each has double dna - 2 chromatids joined by a centromere M - centrioles move to each pole forming a spindle between them - spindle fibres form - chromosomes line up along equator A - double stranded chromosomes spilt into 2 single chromosomes - single chromosomes move to opposite poles T - 2 new nuclear membranes form around the chromosomes - 2 nuclei are formed C - cell cytoplasm splits - 2 new cells form - each with 2 single chromosomes
steps of mitosis
IPMATC
steps of meiosis
IPMATC PMATC
fertilization
- fusion of sperm and egg cell - halves the number of chromosomes from 46 to 23 - resulting cell has 46 each (zygote) - sperm and egg = haploid gametes - zygote = diploid - produces genetic variation - 2 parents
mitosis vs meiosis
mitosis: - cell division for growth and repair - takes place in somatic cells - one cell division - asexual - daughter cell = diploid - no variation - diversity narrowed - produces tissue culture meiosis: - cell division for producing gametes - takes place in gonads/reproductive organs - 2 cell divisions - daughter cell = haploid - sexual - diversity increased - produces new organisms
continuity of life
- for life to continue genetic information must be transferred to the next generation - location of particular genes on a chromosome is referred to as a locus - in homologous chromosomes corresponding genes found in same locus - alternate forms of the same genes are called alleles
the cell cycle
- sequence of events from one cell division to another - life cycle of cell interphase = G1 phase (cell growth before replication), S phase (synthesis & replication), G2 phase (cell prepares for division) M phase = mitosis, cytokinesis G0 phase - withdrawn from cell cycle, not preparing to replicate - terminally differentiated cells e.g. nerve cell - can enter under certain circumstances checkpoints: first - beginning of interphase, pass if the cell is large enough, sufficient nutrients available second - end of interphase, pass if cell is large enough and replication is successful third - pass if all chromosomes attached to mitotic spindle
non - disjunction
chromosome can fail to separate resulting in abnormal numbers of chromosomes in gametes
aneuploidy
- results in abnormal number of sex chromosomes turner syndrome - 1 sex chromosome XO Klinefelter syndrome - 1 extra chromosome XXY trisomy - 1 extra chromosome down - trisomy 21 edward - trisomy 18
mutations
change in gene sequence by adding or deleting nucleotides
causes of mutations
spontaneous - random - errors in replication or division induced - environment - radiation - poison - diet
location of mutations
gametic - in sex cells - affects all cells - inherited somatic - in autosomal cells - harmless or may cause cancer - not inherited
strength of mutations
lethal - deadly harmful - non lethal e.g. down syndrome silent - harmless with no noticeable affect beneficial - useful particularly in new environment
gene mutations
- arise when a gene fails to make an exact copy of itself during replication substitution missense: - produces 1 new amino acid - may change function - changes one nucleotide substitution nonsense: - produces a stop codon - early termination of polypeptide chain - short, disfunctional insertion: frame shift - 1 base is inserted - reading frame shifts resulting in new amino acids rom the point of insertion - resulting protein will be different and non-functional deletion: frame shift - 1 base deletion - can reinsert somewhere else, amino acids between these points change - if not reinserted affects all amino acids after - effects depend on how many amino acids were affected
mutagen
agent capable of inducing a mutation uv rays
chromsome mutations
duplication - extra copy is made of a section of chromosome and inserted into the same or another chromosome inversion - breaks in 2 places and then rotates 180 degrees before rejoining - genes neither gained or lost - still function normally deletion - breaks in 2 places, falling out - leads to absence of genes insertion - piece of chromosome is added translocation - section breaks off and reattaches to another chromosome, non - homologous changes in chromosome number - anapolidy : loss / gain f chromosome - polyploidy : loss / gian of chronometer set
phenotype variation
morphological - variation in shape and structure include internal anatomy biochemical - variation in chemical structure - composition of organisms e.g. proteins, lipids physiological - variation in ways organisms carry out metabolism and maintain their bodily processes behavioral - differences in ways organisms perceive, think and react
punnet squares
- tool used to help predict the outcome of genetic crosses - each outcome has equal chances of occurring
pedigree
- family tree of genetic history square = male circle = female colored in = affected
determine if trait is recessive or dominant (pedigree)
- need to find the triangle - no triangle can’t tell - disease on bottom = recessive - disease on top = dominant
inheritance rules
autosomal recessive : appears in both sexes equally - tend to skip a generation - e.g. cystic fibrosis, sickle cell anemia autosomal dominant : appears in both sexes equally - unaffected parents do not transmit the trait X-linked recessive : affects more males - affected fathers never pass to sons but all daughters are carriers
allele
2 forms of the same gene - dominant - recessive
dominant
- stronger - expressed - shown as capital
recessive
- allele that is masked - shown as lower case
trait
- any characteristic that can be passed from parent to offspring
heredity
passing of traits from parent to offspring
genetics
study of heredity
genotype
gene combination for trait
phenotype
physical feature resulting from genotype
P generation
parental
F1
first filial offspring of P
F2
second filial offspring of F2
locus
specific position of gene on a chromosome
carrier
carry the trait but don’t express the disorder
test cross
unknown dominant phenotype is crossed with the homozygous recessive phenotype
- if homozygous 100% with show dominant phenotype
- if heterozygous 50% will have dominany phenotype
incomplete dominance
offspring show a blend of traits red + white = pink
codominance
- offspring expresses both traits red + white = red and white
sex linkage
- gene on sex chromosome - X linked - males have higher chance of getting it - mutations include colour blinders, muscular dystrophy
monogenic
- characteristics determined by 1 pair of genes e.g. Ee
polygenic
- more then one gene
- phenotype shows variation
- environment also influences phenotype
- eg weight
blood types
Type A: AA, AO - donate to A, AB - get from A,O Type B: BB,BO - donate to B, AB - get from B,O Type AB : AB - donate to AB - get from anyone Type O : OO - donate to anyone - get blood demo O (lower case i)
multiple alleles
more then 2 different forms of the same gene
continuous vs discontinuous variation
continuous - range of measurements e.g. height discontinuous - certain categories e.g. blood
