Sexual Reproduction

Question 1

what is fertilisation

Answer 1

union of male and female gametes

Question 2

what does fertilisation provide

Answer 2

recombination of paternal and materanl genes
restores diploid number

Question 3

what happens once egg and sperm fuse step by step

Answer 3

1) sperm disconnects from flagellum
2) sperm nucleus migrated to female pronucleas
3) fuse
4) forms diploid nucleus
5) fertilisation
6) zygote forms

Question 4

what are early cell divisions called

Answer 4

cleavages

Question 5

what does the SRY (sex-determining region Y) do

Answer 5

-gene on Y encodes for transcription factor that induces testicular development
-induces expression of Sox9 transcription factor

Question 6

negatives of sexual reproduction (vs asexual)

Answer 6

-maintain molecular machinery
-find mating partner
-decreased reproductive capacity

Question 7

benefits of sexual repro

Answer 7

-genetic variability helps species adapt to environment
-advantageous alleles brough together
-paired chromosomes allow mutations to be masked

Question 8

what are the male and female germ cell gametes

Answer 8

male = sperm or spermatozoa
female = secondary oocyte

Question 9

Meoisis gamete

Answer 9

haploid chromosome number

Question 10

fertilisation gamete

Answer 10

dilpoid choromosome number

Question 11

whats a gamete

Answer 11

sex cell

Question 12

what happens in Meiosis 1

Answer 12

-separation of homologous chromosomes
-genetic cross over

Question 13

what happens in meiosis 2

Answer 13

-separated of paired chromatids

Question 14

describe the process of meosis in full

Answer 14

1) undifferentiated germ cell replicated
2) forms two chromatids
3) homologous chromosomes paired
4) Crossing over and recombination
5) Forms bivalent
6) Metaphase1
7) Cell division 1
8) metaphase 2
9) Cell division 2
10) 4 haploid cells

Question 15

When does mitosis occur in females in sexual reproduction

Answer 15

before birth

Question 16

describe process that occurs to set female up for meiosis

Answer 16

1) Oogonium undergoes mitosis
2) Primary oocyte arrests in prophase 1

(mitosis)

Question 17

what happens after puberty after mitosis and birth

Answer 17

1) Secondary oocyte polar body of 1n
2) arrests in metaphase 2
3) Ovulation and sperm entry
4) Sperm fuses to 1n
5) Meiosis and fertilisation
6) fertilised egg

Question 18

what does crossing over lead to

Answer 18

recombinant chromatids
mix of both homologues

Question 19

what does crossing over mean in terms of inheritation

Answer 19

crossing over = incomplete linkage of genes on same chromosome
alleles on same chromosome not inherited together

Question 20

what does crossing over result in

Answer 20

offspring with recombinant phenotype

Question 21

what is the recombination frequency of genes

Answer 21

1 centomorgan (cM) = 0.01 frequency recombination

Question 22

are recombination frequences linear

Answer 22

not linear to physical distances
ends of chrom higher crossover rate
single chrom has multiple crossovers

Question 23

what is a genetic map

Answer 23

represents gene locations on a chromosome

Question 24

how is the relative distance between genes determined

Answer 24

how often crossing over occurs between them during meiosis

higher recmbination = further apart

Question 25

what is linkage

Answer 25

genes located close together on chromosome are linked and have lower recombination frequency

Question 26

Alfred Sturtevant proposed what

Answer 26

using recombination frequency to map genes on a chromosome

Question 27

if a father has an X-linked recessive condition what will his daughter and son inherit

Answer 27

daughter carries son unaffected

Question 28

if mother has x linked recessive what do her children inherit

Answer 28

50% passing it onto son and daughter

Question 29

Word for when genes are on the X chromosome of a male

Answer 29

hemizygous

Question 30

Where do males and females inherit there chromosomes from

Answer 30

Males = inherit X from mother Females = inherit one X from mother one father

Question 31

what kind of trait is colour blindness

Answer 31

X linked recessive trait

Question 32

why is colour blindness more affected in males

Answer 32

Males have XY so they dont have dominant X to overcome recessive gene

Question 33

what is aneuploidy

Answer 33

abnormal number of chromosomes in an organism

Question 34

Why does aneuploidy arise

Answer 34

non-disjunction failure to separate homologous chromosomes during meiosis

Question 35

how many of conceptions end in abortion

Answer 35

50%

Question 36

how many abortions are due to chromosonal abnormalities

Answer 36

50%

Question 37

how many conceptions end in abortions due to chromosonal defets

Answer 37

25%

Question 38

How many birth effects are from chromosonal abnormalities

Answer 38

7%

Question 39

what does meiosis create

Answer 39

haploid gametes