Chapter 10, 11.1 and 12.4 - Meiosis and Chromosome Disorders Flashcards
Define gene
Unit of hereditary information consisting of a specific nucleotide sequence in DNA (or RNA in some viruses)
Define Gametes
Haploid reproductive cells formed by meiosis or descended from meiosis-formed cells (like eggs & sperm). They unite in sexual reproduction to produce a diploid zygote.
Define locus
Specific place along the length of a chromosome where any given gene is (LOCation = LOCus)
Define somatic cell
Any cell in the body of a multicellular organism EXCEPT gametes
Asexual vs sexual reproduction DIFFERENCES
Ace - 1 individual is sole parent, all genes passed down, produces clone, can involve prokaryotes
Ce (i’m clever aren’t i) - 2 parents, unique mixed gene combo, no clone
Asexual and sexual reproduction SIMILARITIES
Parent(s) pass down genetic information, can involve eukaryotes, more beings made
How does a hydra do asexual reproduction? (it’s a real thing not the mythological beast although that’s probably where it came from)
Budding - grows a mass of mitotically dividing cells that become a small hydra and detach from the parent
How do redwoods do asexual reproduction?
Umm… idk but they all come from a single parent tree… (:>
What type of reproduction will give you clones?
Asexual unless mutated
What is a life cycle in a genetic sense?
A generation to generation sequence of stages in the reproductive history of an organism.
- During meiosis, a cell with the diploid number of chromosomes splits
- It becomes a gamete with the haploid number of chromosomes
- It stays that way until fertilized - then it becomes a zygote with the diploid number
What are homologous chromosomes?
A pair of chromosomes with the same length, centromere position, staining pattern, and type of genes at the same loci (the information might not be the same, so they aren’t truly identical and they’re not sisters). 1 chromosome comes from each parent to make up the pair.
How many chromosomes does each human cell have, and how many homologous pairs?
46 in somatic cells, 23 in gametes, 23 homologous pairs in somatic cells (gametes don’t have those)
What is a sex chromosome?
X and y chromosomes - X is big and y is small and they have info not found on the other and they determine sex and also x or y linked traits
How many sex chromosomes in human somatic cell?
2
What is an autosome?
Chromosomes that determine pretty much everything but sex and x and y linked traits. They pair up.
How many autosomes in a human somatic cell?
44
What is a karyotype?
A display of condensed chromosomes arranged in pairs to screen for defective or abnormal chromosome numbers
Process of a karyotype creation
somatic cell –> drug –> mitosis –> stop it at metaphase –> stain –> use a microscope and a camera and some software to organize –> you get to see the karyotype!
In which phase of the cell cycle are chromosomes removed from a cell when making a karyotype? Why then?
Metaphase because that’s when the chromosomes are the most condensed
3 things that can be determined from a karyotype
- Defective chromosomes
- Abnormal # of chromosomes
- Sex (if you didn’t know that already)
Hap or dip: Liver cell
Dip
Hap or dip: Egg
Hap
Hap or dip: Skin cell
Dip
Hap or dip: Gamete
Hap
Hap or dip: Zygote
Dip
Hap or dip: Sperm
Hap
Hap or dip: Somatic cell
Dip
Hap or dip: Sex cell
Hap
T or F: Homologous chromosomes are connected between interphase and meiosis 1
False, they’re floating around with their sisters but not their homologous partner
ll || || ll
How many chromosomes in this cell? How many homologous pairs? How many chromatids?
4 chromosomes, 2 homologous pairs, 8 chromatids
What is a zygote?
A fertilized egg
Meiosis purpose
Divide a diploid cell into 4 haploid gametes (you duplicate to get 4n then go back to 2n then just n) that can be fertilized and used in sexual reproduction
Meiosis vs fertilization (use your thinking brain :D)
Meiosis is the division from 2n in one cell to 4n in 4 cells, fertilization adds another n to gametes to get 2n
What is an allele?
Alternative versions of a gene that may have different effects - for example, an allele for freckles and a homologous chromosome with an allele for no freckles
What happens during meiosis interphase? (SUMMARY)
The pair of homologous chromosomes duplicate (4n total)
What happens during Meiosis 1? (SUMMARY)
Duplicated chromosomes cross over, homologs separate (2n in 2 cells, haploid but with 2x the same info)
What happens during Meiosis 2? (SUMMARY)
Sister chromatids separate (1n in 4 cells)
Summarize prophase 1 of meiosis
Chromosomes condense, cross over at chiasmata, microtubules attach to kinetochores and homologous pairs to move them into the metaphase plate (though that last part gets into metaphase 1)
~~~~~~~~ –> –
——–;;-;;——-
What is crossing over?
Crossing over is when DNA molecules of nonsister (homologous) chromatids are broken by proteins and rejoined together. This exchange of genes and mixed up DNA increases genetic variability
\/ \/ –> \ X /
/\ /\ / X \ —> Now they separate and are mixed up :)
What is the Chiasma (plural chiasmata)
Where the chromosomes intersect (unless textbook was lying and so was google) (a certain someone misled me and I’m salty)
What is the synapsis/synaptonemal complex?
The pairing of one duplicated chromosome to its homolog in a zipper-like structure composed of proteins ___________
……………VVVVVVVVV
……………—————-
How is chromosome arrangement in metaphase 1 different from metaphase in mitosis?
INDEPENDENT ASSORTMENT and homologous chromosomes lined up at metaphase plate like ::::::: instead of ………
What separates in the first division in meiosis 1?
Homologous chromosomes (that have crossed over and independently assorted)
If a cell with 12 chromatids undergoes meiosis 1, how many chromosomes will be in each cell at the end of the first meiotic division?
3
ll ll ll
Are the daughter cells of meiosis 1 haploid or diploid?
2 haploid cells with duplicated information
What separates during meiosis 2?
Sister chromatids
End result of meiosis 2
4 daughter cells that are haploid with unduplicated chromosomes
How many divisions occur in meiosis?
2
What happens to chromosome number in meiosis
divides in half
during which division is chromosome number reduced
Meiosis 1 (from 2x2n to 2xn and then you just get n but l and ll are both chromosomes)
How many times do chromosomes duplicate in meiosis?
1
What 3 things are unique to meiosis (not incl. having 4 daughters or making gametes)?
Synapsis and crossing over (sis chromatids connected by cohesions align lengthwise and nonsis chromatids are broken. Synap. complex forms to attach homologs, dna breaks close up, synap. complex breaks but homologs stay attached (somewhat) and condense) (sarah I am so sorry)
Alignment of homologous chromosomes (independent assortment)
separation of homologs (gives duplicated sister chromatids that are still attached)
Role of mitosis vs role of meiosis
mitosis grows and repairs and allows for asexual reproduction, meiosis makes gametes
T or F: same number of dna replications in mitosis and meiosis
True - 1
What is independent assortment?
2+ genes can assort independently - each pair of alleles segregates independently of any other pair during gamete formation
A B C or A C B
A B C A C B
(is this card redundant? yes. Do I care? absolutely not.)
How can independent assortment lead to variation?
alleles combine randomly - exponentially many combinations and variation
Pic of how it works
AA BB
AA BB
. |
v
AA | BB
AA | BB
|
v
|AA | AA | BB | BB|
AA BB
BB AA
|
v
AA | BB
BB | AA
|
V
|AB | AB | BA | BA|
how does crossing over increase genetic variety?
produces recombinant chromosomes with different genes from 2 different parents
How does random fertilization lead to variety in a population?
Random gametes fertilize other random gametes to make random zygotes for EVEN MORE potential combinations
why is genetic variation important in a population regarding evolution and survival
Leads to helpful mutations to increase survival odds and those get passed down
What is the name of the cell that divides and makes sperm? Hap or dip?
Spermatogonial stem cell - dip (hap is not possible)
AAAAAAAAaaaaaaaaaaaAAAAAAAaaaaaaAAAAAAAAAaaaaaaaaaaaaaAAAAAAAAAaaaaaaaaaaaa
OOOOOOOOOOOOooooooooooooooooOOOOOOOooooooooOOOOOOOooooooooooOOOOOoo
Where does spermatogenesis occur?
seminiferous tubule in testes
how many viable sperm produced at the end of meiosis 2?
2
how many chromosomes in each sperm? What other organelle is in it?
23, acrosome (maybe - might not be acrosome)
At birth how many eggs in female ovaries?
1-2 million (i think)
What phase are a 5-year-old’s eggs in?
Prophase 1 - they mature starting at puberty
What does FSH (follicle signaling hormone) do in oogenesis?
Stimulates a few follicles to resume growth and development
How many eggs produced after meiosis 2?
1 (and a few polar bodies that are insignificant)
If you’re looking at a woman’s polar bodies, can you tell if she has a mutation for a disease gene in her egg?
Yes…? because sister chromatids are identical……? Unless homologous chromosomes had nothing and that formed a polar body but is that even a thing???? I DON’T KNOW I’M SORRY
What is nondisjunction?
When the chromosomes don’t split right, leaving too many in one cell and too few in another
What happens if nondisjunction happens during Meiosis 1?
all 4 daughters have defects - 2 with triosmy, 2 with monosmy
What happens if nondisjunction happens during Meiosis 2?
2 daughter cells have defects - 1 triosmy, 1 monosmy
Which is worse - meiosis 1 or 2 nondisjunction
1 bc you mess up 4 gametes instead of 2
What is aneuploidy?
A chromosomal defect where there’s an abnormal number of 1 or more chromosome(s)
What is monosmy?
Missing a chromosome (n-1 in the cell)
What is triosmy?
Extra copy of chromosome (n+1 in the cell)
What is polyploidy?
Having more than 2 complete chromosome sets in all somatic cells
What is down syndrome? How do you test for it prenatally?
Extra chromosome 21 - leads to facial features, short statures, heart defects, and developmental delays, but you can be alive with it. Use amniocentesis (test amniotic fluid) to look at their chromosomes and see if they have it
What is Klinefelter Syndrome?
XXY (nondisjunction caused that) - make sex organs, sterile, some female body characteristics
What is Turner syndrome?
Monosmy X (caused by nondisjunction) - just 1 x chromosome - female, no sex organs develop (unless you do estrogen replacement therapy)
What is Triosmy X?
XXX - female, slightly taller than average, fertile, can be at risk for learning disabilities
What is Cri du Chat?
Deletion in chromosome 5 - intellectually disabled, smaller head, unusual cry, usually die very young
What is chronic myelogenous leukemia?
Tips of chromosomes 9 and 22 switch (how did they manage that?) - the fused gene leads to uncontrolled cell cycle progression
What is deletion and how does it alter chromosome structure?
Chromosomal fragment is lost - organism missing certain genes (often lethal)
What is duplication and how does it alter chromosome structure?
broken fragment may get reattached as an extra segment to a sister or nonsister chromosome - now another cell doesn’t have genes and this one has too many
What is inversion and how does it alter chromosome structure?
Chromosomal fragments reattach in reverse orientation - gene expression is messed up
What is translocation and how does it alter chromosome structure?
Fragment joins a nonhomologous chromosome (may or may not be reciprocated) - gene expression messed up
T or F: A person with XXY is male
True
T or F: A person with only X is female
True
What is triosmy 18 called?
Edward’s syndrome
