Question

Also, discuss how color-blindness occurs based on the physiology of sight. Describe the process of inheritance. Describe the chromosomal basis of Mendel’s laws of segregation and independent assortment. How do X-linked genes pass traits from one generation to the next?

Answer 1

colour blindness occures when light sensitive cells in the retina fail to respond appropriately to variations in wavelength of light that enable people to see an array of coloures . it is a genetic condition caused by difference in how one or more light sensitive cells found in the retina of the eye respond to certain coloures cones contril colour vision . cones have varius pigments called colour pigments if there is problem with this pigments colourblindness occures ; this problem is an inherited one . usually when cone perceives light and stimulated ,the brain interprets this signal and the colour of the object identified in this disease . fault may occur within cone cells or in the pathway of signal

deuteranomaly -- when the green cone photopigment does not work yellow and green look redder

protanopia--not working red cones ,colour looks like dark grey

deuteranopia --not working green con cells ,green look like beige

tritanomaly - blue cones work in a limited way ,blue looks greener

tritanopia --no blue cone cells ,blue looks green

in complete colour blindness or monochromacy dont see any colour , it is associated with nystagamus

in rod monochromacy none of cone cells work as a result everything appears in black and white

colour blindness is passed from mother to sun on 23 rd chromosome which is sex chromosome red green colourblindness is sex linked recessive and blue yellow is autosomal dominent

chromosomal theory of inherittance states that individual genes are found at specific location of chromosomes and that thr behaviour of chromosomes during meosis can explain why genes are inherited according to mendels law

observation support this theory includes

law of seggregation --the members of a homologous pair seperate in meosis ,so each sperm and egg receives just one number .this process mirrors seggregation of alleles in to gamates in mendels law of seggregation. this is mendels first law by correns , or law of non mixing of alles , or purity of gamates .here two alles of a gene controlling each character stay together in individual , during gamate formation or meosis alles of a pair seggregate from each other ,so that a gamate carries only one alle of character .if Tt is genotype of a parent ,the gamate formed are t,T

law of independant assortment -- the members of different chromosome pairs are sorted in to gametes independantly of one another in meosis just like the alleles of different gene in mendels law of independent assortment it also known as mendels second law of correns .here the alles of two pairs of traits seperate independantly of each other during gamate formation . in case of pea plant dihybrid cross the round yellow wriinkled green trait each alle round ,green, wrinkled , and yellow seperates independantly during gamate formation

these get randomly rearranged in the offspring at the time of fertilization producing both parental and new combination of traits

x linked inheritance THE GENE CAUSING TRAIT OR DISORDER LOCATED ON X CHROMOSOME ,CIS GENDER FEMALES HAVE TWO X CHROMOSOME WHILE CISGENDER MALES HAVE ONLY ONE X CHROMOSOME

2TYPES X LINKED DOMINENT AND X LINKED RECESSIVE

IN X LINKED RECESSIVE THE MUTATION IN A GENE ON X CHROMOSOME CAUSE PHENOTYPE TO BE ALWAYS PRESENT IN MALES AND FEMALES WHO ARE HOMOZYGOUS FOR THE GENE MUTATION FEMALES WITH ONE COPY OF MUTATED GENES ARE CARRIERS

X LINKED DOMINENT INHERITANCE REFERS TO GENETIC CONDITIONS ASSOCIATED WITH MUTATION IN GENES ON X CHROMOSOME .A SINGLE COPY OF MUTATIONIS ENOUGH TO CAUSE DISEASE IN BOTH MALES AND FEMALES