OVERALL HARD TO REMEMBER

Question 1

How do we sequence genomes?

Answer 1

1) DNA is sliced up
2) Coloured florescent markers are used to mark the DNA copies, a different colour marker is used for each sequence ending in each of the different bases.
3) The samples are mixed together and all the DNA copies are separated in one lane of a gel according to the number of nucleotides.
4) A laser scans along the lines to make the markers show up.
5) An optical detector is used to detect the colours
6) A computer sequences the genome

Question 2

How is starch absorbed?

Answer 2

Amylose has bonds between the 1 and 4 carbons, amylase breaks these bonds as long as there is a chain of at least 4 glucose monomers.
Amylose is therefore digested into a mixture of two and three glucose fragments called maltose and maltriose.

Amylopectin is a branched form of amylose, amylase cannot break the 1,6 bonds. These sections that cannot digest are called dextrins. Dextrinase therefore has to break these down. Maltase and maltotiose digest the two forms of broken down amylose and then dextrinase takes care of the rest.

Question 3

The menstrual cycle?

Answer 3

1. Follicular Phase

Follicle stimulating hormone (FSH) is secreted from the anterior pituitary and stimulates growth of ovarian follicles
The dominant follicle produces estrogen, which inhibits FSH secretion (negative feedback) to prevent other follicles growing
Estrogen acts on the uterus to stimulate the thickening of the endometrial layer

2. Ovulation

Midway through the cycle (~ day 12), estrogen stimulates the anterior pituitary to secrete hormones (positive feedback)
This positive feedback results in a large surge of luteinizing hormone (LH) and a lesser surge of FSH
LH causes the dominant follicle to rupture and release an egg (secondary oocyte) – this is called ovulation

3. Luteal Phase

The ruptured follicle develops into a slowly degenerating corpus luteum
The corpus luteum secretes high levels of progesterone, as well as lower levels of oestrogen
Estrogen and progesterone act on the uterus to thicken the endometrial lining (in preparation for pregnancy)
Estrogen and progesterone also inhibit secretion of FSH and LH, preventing any follicles from developing

4. Menstruation

If fertilisation occurs, the developing embryo will implant in the endometrium and release hormones to sustain the corpus luteum
If fertilisation doesn’t occur, the corpus luteum eventually degenerates (forming a corpus albicans after ~ 2 weeks)
When the corpus luteum degenerates, estrogen and progesteron levels drop and the endometrium can no longer be maintained
The endometrial layer is sloughed away and eliminated from the body as menstrual blood (i.e. a woman’s period)
As estrogen and progesterone levels are too now low to inhibit the anterior pituitary, the cycle can now begin again

Question 4

Where are the menstrual hormones produced?

Answer 4

PITUITARY GLAND - FSH LH

OVERIAN HORMONE - OESTROGEN AND PROGESTERONE

Question 5

How does IVF happen?

Answer 5

The women is given medication to stop FSH and LH because FSH makes oestrogen and LH makes progesterone so it stops it all. Then the woman is injected with FSH to make loads of follicles which are washed out.

Question 6

Electron acceptors in photosynthesis?

Answer 6

2 - plastoquione
1 - plastocyanin
1 - ferodoxin