Meiosis Flashcards
Meiosis doesn’t take place in all eukaryotes. True or false?
False - it is important for sexual reproduction and takes place in all eukaryotes
Does meiosis produce haploid or diploid gametes?
Haploid
Why do male and female gametes need to fuse during fertilisation?
As meiosis produces haploid gametes, they need to fuse to create a new diploid cell known as a zygote
Meiosis is known as reproductive or ______ division
reductive
diploid cells (2n) produce ____ (n) gametes
4 haploid
what must happen to the DNA before meiosis can begin?
DNA must be replicated (just like in mitosis)
At what stage of meiosis does recombination take place?
Prophase 1
Meiosis 2 involves separation of __________
sister chromatids
Crossing over (during recombination) requires close alignment of homologous pairs of chromosomes known as _______
bivalents
What is the name given to the junctions that are formed as a result of crossing over?
Chiasmata
Chiasmata allows small sections of chromosomes to be exchanged between ___________ sister chromatids
non-homologous
What is the significance of meiosis?
facilitates sexual reproduction
genetic variability in gametes
recombination and independent assortment allow for a greater diversity of genotypes in the population
Which stage of meiosis dominates?
Prophase 1
Sister chromatids separate during meiosis 1. True or false?
False - they separate during meiosis 2
What does disjunction mean?
The normal separation of chromosomes
If separation of chromosomes is not normal, it’s called _________
nondisjunction
What does Klinefelter Syndrome result in?
An extra X chromosome in males
What does Turner Syndrome result in?
Only one X chromosome in females
Who does the XYY Syndrome affect?
males
Gamete production in females is called _______
oogenesis
In females, meiosis occurs in precursor cells known as _______ that divide twice to produce the ________
oogenia
oocytes
Oocytes stop at an early stage of meiosis 2 and lay dormant within the ovaries inside a layer of somatic cells called the follicle. True or false?
False - early stage of meiosis 1
During the menstrual cycle in females, follicles produce mature _________ which continue meiosis 1 and arrest at meiosis 2 until fertilisation or menstruation
oocytes
What is gamete production in males called?
Spermatogenesis
In males, meiosis occurs in stem cells known as ________
spermatogonia
Spermatogonia divide twice to become __________
spermatozoa
Where are the spermatogonia found?
outer cortex of the seminiferous tubules of the testicles
Sperm are made continuously but most are malformed. True or false?
True
For successful fertilisation, the ejaculate must contain at least _____ normal sperm
15%
Smoking reduces the chances of conceiving by _____
10-40%
Smoking can age a woman’s body clock by 10 years. True or false?
True
Men who smoke have lower sperm counts and more malformed sperm than non-smokers. True or false?
True
Genetic defects in sperm can accumulate but cannot be passed on to children. True or false?
False - they can be passed on
Effect on fertility is down to nicotine so nicotine patches reduce the chances of these problems happening. True or false?
False - nicotine patches can cause similar problems
