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possible questions for bio wa2 - Coggle Diagram
possible questions for bio wa2
cell division
mitosis
what happens during [interphase]?
meiosis
what are the causes of variation?
crossing over of homologus chromosomes in prophase l, random assortment of chromosomes, random fertilisation of gametes
prophase 1: 46 metaphase 1 (within a cell): 46 anaphase 1:46--> 23 at the end
chromatids are fully fucntional on their own
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compare meiosis and mitosis
similarities:
both involve the formation of spindle fibre
boh involves dividion of nuclear content
both involve chromatin condensing to chromosomes
both involve the formation of new cells
differences:
in mitosis, homologous chromosomes do not pair up in prophase. in meiosis, homologous chromosomes pair up in prophase l
in mitosis, chromosomes form one row at the equator of the spindle during metaphase. in meiosis, homologous chromosomes form 2 rows at the equator of the spindle during metaphase l. chromosomes form 1 row during metaphase ll.
in mitosis, the nucleus divides once, but in meiosis, there are 2 sucessive nuclear divisions
inheritance
compare discontinuous varation and continuous variation
continuous variation deals with a range of phenotypes, whereas discontinuous variation deals with a few clear-cut phenotypes
continous variation is greatly affected by the environment whereas discontinous variation is realtively unaffected by the environment
continuous variation is controlled by many genes whereas discontinous variation is controlled by one or a few genes
in continous variation, the differences between individuals are quantitative. there is a continuous range of intermediate values and every possible form between the 2 extremes will exist. in discontinuous variation, the differences between individuals are qualitative. there are discrete groups without intermediate forms
describe the characteristics of a x-linked recessive
in an x-linked recessive, usually more males than females are affected. no offpsring of an affected male are affected, causing the trait to skip generations in the pedigree; but is always with an unaffected female in the intermediate generation
give examples of continuous variation
height, body mass, skin color, intelligence
describe the characteristics of a x-linked dominant
when the male carries the affected x chromosome, all the female offspring will be affected but no male offspring will be affected. aprroximately half of the offspring of affected females are affected regardless of sex
give examples of discontinuous variation
tongue rolling ability, blood group, single or double eyelid, albinism
skill: how do we tell if a phenotype is recessive or dominant:
if the trait is recessive, it tend to skip generations. an individual who is affected may have parents who are unaffected (carriers). all the children of 2 affected parents. if the trait is dominant, every affected individual has at least one affected parent. affected individuals who mate with unaffected individuals have a 50% chance of transmitting the trait to each child.
what are mutations?
mutations are a sudden or spontaneous change in the sequence of gene, chromosomes or a change in in chromosomal number (which results in the change of a phenotype of an organism)
skill: how to tell if a parent is heterozygous or homozygous
look at the children. are they affected or unaffected? 2. look at the parents. are they unaffected or affected? 3. are there unaffected or affected siblings? there are many possible combinations of genotypes in pedigrees, so it is usually looked at on a case to case basis
what is a gene?
a gene is a unit of inheritance that has a specific sequence of nucleotides, as a part of a dna molecule that contains information to make a polypeptide. (passed down from parent to offpsring via the parents chromosomes of the parents gametes)
what is an allele
an allele is a form of a gene that can have multiple variations.
skill: drawing of genetic diagram
-remember to write the key, and label the gametes and random fertilisation. if a trait is sex-linked, state that the female is xx and the male is xy. no sex-linked trait is on the y chromosome. remember to state the phenotypic ratio (should be simplified). use ruler for random fertilisation table.
if the question asks to predict or show a certain truth about the showing of genes in the offspring, consider possibilities for the already given trait. e.g. codominance genotype in blood group would be the mating of l^al^a and l^bl^b. take note of which traits are determined by homozygous recessive. when comparing the ratios write the phenotype in its full name.
do not use different alpahbets for contrasting traits. e.g. if the dominant allele for black coat is x^B, the recessive allele for ginger coat is x^b. remember to label in the random fertilisation table which gametes belong to the female and the male respectively.
what are the causes of variation
meiosis, fertilisation, mutation
molecular genetics (pg 15-21)