OCR Biology F215 Control, Genomes and Environment Fri 15 June 2012

Original post by Obadetona

How would you know duplication isn't just insertion?

Insertion = 1 extra base added
Duplication = 1 or more base

Reply 1981

Original post by Bi0logical

Insertion = 1 extra base added
Duplication = 1 or more base

ask me question :wink:

please

Reply 1982

Revent

10

Original post by KeepBreathing

Just finished a past paper I'd already done and got 72/100, even though I'd already done it before and got 68 that time. What the? Just watch OCR screw us all over with the grade boundaries this year.

Don't know about OCR, but I suggest you go over what you got wrong :p:

Getting 72/100 in a second attempt means there must be a topic that you're finding particularly difficult/haven't learnt properly. I'm just hoping the grade boundaries stay the same. Need 144ish for an A*!! :eek:

Reply 1983

I already know I'm gonna fail this exam :frown:

Reply 1984

Original post by otrivine

ask me question :wink:

please

How does Meiosis produce cells that are genetically different? (8)

Reply 1985

Original post by Bi0logical

How does Meiosis produce cells that are genetically different? (8)

MATE DONT SAY THAT YOU ARE SO SMART ! NEVER SAY YOU WILL FAIL SAY I KNOW I CAN 100% GET AN A************************

you want me to describe the whole metaphase prophase business? :wink:

Reply 1986

How much raw marks would around 106 UMS be?

Reply 1987

Original post by otrivine

MATE DONT SAY THAT YOU ARE SO SMART ! NEVER SAY YOU WILL FAIL SAY I KNOW I CAN 100% GET AN A************************

you want me to describe the whole metaphase prophase business? :wink:

Haha! Okay HOPEFULLY I'LL GET AN A* !!!
Anyway, I was asking how Meiosis produces cells that are genetically different?

So what happens during the stages of Meiosis that causes the genetic differences, pretty tough question:P

Reply 1988

KeepBreathing

Original post by Bi0logical

How does Meiosis produce cells that are genetically different? (8)

Thought I'd have a go since I haven't revised this in a while.

Crossing over of chromosomes in prophase I
When homologous chromosomes line up at the equator of the cell, they form a bivalent (pairs of chromosomes with one from each parent). Non-sister chromatids adjacent to one another twist around each other and genetic information from each is passed between the chromosomes. This results in genetically different cells because although the genes remain the same, alleles are inherited from each parent. So each chromosome has the same genes but different alleles than it originally had.

Independent assortment of chromosomes in metaphase I
Different combinations of maternal and paternal chromosomes go into each cell. Therefore a different combination of alleles is inherited every time. Linkage occurs when alleles are on the same chromosome and so are inherited together.

Independent assortment of chromatids in metaphase II
Much the same as in metaphase I, different combinations of maternal and paternal chromatids go into each cell. Therefore a different combination of alleles is inherited each time.

....Lots of blagging there!!! And certainly not enough for 8 marks haha.

Reply 1989

kimmey

Original post by Bi0logical

How much raw marks would around 106 UMS be?

maybe about 58ish

Reply 1990

Original post by Bi0logical

Haha! Okay HOPEFULLY I'LL GET AN A* !!!
Anyway, I was asking how Meiosis produces cells that are genetically different?

So what happens during the stages of Meiosis that causes the genetic differences, pretty tough question:P

there is prophase I where chromatids attach at points called chaismata and form bivalents and is where crossing over takes place and legth of chromatid is swapped with other.chromotids shorten and chromosomes thicken
Metaphase I is where the homologous chromosomes line up at the equator of the cell
and each members of homologous chromosomes are opposite poles.
Anaphase I is where the homologous chromomes are pulled apart and are chormatids.
Telophase I is where Cell divides and nuclear envelope reforms,
Prophase II is where chromosomes shorten and nuclear envelope breaks
Metaphase is where chromosomes are lined up at equator
Anaphase II is where chromosomes are pulled apart in opposite poles
TelophaseII is where cell divides and chromosomes reforms
mutation
reassortment of chromosomes
independent assortment (metaphaseII)

(edited 11 years ago)

Reply 1991

Sparkzz

4

Original post by Bi0logical

Haha! Okay HOPEFULLY I'LL GET AN A* !!!
Anyway, I was asking how Meiosis produces cells that are genetically different?

So what happens during the stages of Meiosis that causes the genetic differences, pretty tough question:P

Quite a few things occur. Crossing over during prophase I where parts of DNA are exchanged being non-sister chromatids; this results in a new combination of alleles hence increasing genetic variation. Independent assortment due to the random distribution of the maternal and paternal chromosomes in a homologous pair at metaphase I and their subsequent segregation at anaphase I. Independent assortment due to the random distribution of sister chromatids at metaphase II and their subsequent segregation at anaphase II. Random DNA or chromosome mutations.

This was posted from The Student Room's iPhone/iPad Ap

Reply 1992

sumsum123

2

Original post by Revent

Don't know about OCR, but I suggest you go over what you got wrong :p:

Getting 72/100 in a second attempt means there must be a topic that you're finding particularly difficult/haven't learnt properly. I'm just hoping the grade boundaries stay the same. Need 144ish for an A*!! :eek:

I need 143 "/ . Any idea how many raw marks needed for that?

Reply 1993

kimmey

Original post by sumsum123

I need 143 "/ . Any idea how many raw marks needed for that?

maybe about 76

Reply 1994

Original post by otrivine

there is prophase I where chromatids attach at points called chaismata and form bivalents and is where crossing over takes place and legth of chromatid is swapped with other.chromotids shorten and chromosomes thicken
Metaphase I is where the homologous chromosomes line up at the equator of the cell
and each members of homologous chromosomes are opposite poles.
Anaphase I is where the homologous chromomes are pulled apart and are chormatids.
Telophase I is where Cell divides and nuclear envelope reforms,
Prophase II is where chromosomes shorten and nuclear envelope breaks
Metaphase is where chromosomes are lined up at equator
Anaphase II is where chromosomes are pulled apart in opposite poles
TelophaseII is where cell divides and chromosomes reforms
mutation
reassortment of chromosomes
independent assortment (metaphaseII)

Yeah you included the right stuff but waffled in the middle.

This is what you should talk about;
- Crossing over of chromatids
- Independent assortmnet of chromosomes (in metaphase I)
- Independent assortment of chromatids (in metaphase II)

and explain each point.

Reply 1995