Chapter 14 C Further Complications Of Mendel Flashcards
After studying sex chromosomes where did the X and Y chromosomes suggest humanity originated
Africa
What determines a sex of an animal
Sex chromosomes
Provide the different combinations of sex chromosomes
XX - female
XY - male
YY - not possible and deadly
What is YY combo not possible and deadly
The X chromosome makes essential proteins for humans to surivie
What is the gene called in the Y chromosome that trigger male development
The gene is called SRY
How many genes does the X chromosome carry?
1000 genes
How many genes does the Y chromosome Carrie
50
Why is it more common for males to have a recessive gene disorder
No allele can mask the Y. The Y is much shorter than the X chromosome.
What are examples of disorders common in males due to sex-linked traits
Red-green colour blindness and hemophilia.
How many more times is hemophilia more common in males than in females
8 times more common
What is X-inactivation and the possible complication.
Normally in females only one X chromosome is active (able to be transcribed) in each cell. The other X condenses into an inactive Barr Body. Which X shuts down in each is random. Meaning if female is heterozygous (carrier) 1/2 of one allele can be expressed and the other 1/2 can be expressed.
Name an example of x-inactivation
Calico cats. x inactivation occurs when the cats are still embryos in each early skin cell. Through mitosis they produce patch of clones that express the colour determined by the X chromosome that is still functional
Does Y chromosomes have anything special. Explain your reasoning.
Nothing much, they only really carry maleness and some types of impaired fertility because there are not a lot genes in Y chromosomes (50)
Why can the ancestry of male’s Y chromosomes be traced relatively easily?
The Y chromosome stays relatively the same throughout generations cause there is no crossing over between X & Y chromosomes. The only changes present in the Y chromosome would be a mutation
How can a Y chromosomes give us clues to where people originated
Each time a mutation occurs in the Y chromosome it creates a new Y- chromosome haplotye. The distribution of Y chromosome haplotypes throughout history indicate the that human spread out of Africa
What are linked genes
When alleles for genes travel on the same chromosome as result there is less variation.
Linked genes is when alleles for genes travel on the same chromosome does that mean Mendel was wrong?
No, Mendel was lucky. the characters (genes) he studied are all on different pairs of chromosomes
Define genetic recombinant
It means an individual with different combinations of traits (phenotypes) than either parent
When are genetic recombinants common
If the genes are unlinked.
If only ~17% chance of offsprings are recombinants in fruit flies. What is another reasons ‘surprise’ combinations occur
Crossing over
How does crossing over affect an animals genetics
Crossing over occurs in prophase 1 of meiosis. When chromosomes pairs do an exchange of their parts. This would alter an animals genetic make up if the alleles were heterozygous.
Where does the crossing over break occur?
It’s random but there is higher chance it would occurs between genes that are farther apart in a chromosome. the distance between genes is correlated with the frequency of genetic recombinants
What is frequency of combination of two genes range. Explain
0% - crossing over never takes place or when genes are right next to each other
50% - genes are so far apart that crossing over between genes always takes place
