Genetics I: Meiosis and Mutations
Terms and Information:
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sexual reproduction- use of (**) to reproduce; necessary to have 2 different cells
(**) - sex cells; sperm and egg; haploid
somatic cells- an organism’s (**); diploid
(**)- having one set of xsomes; gametes
(**)- having 2 sets of xsomes; somatic cells
I. Meiosis- 2 stages of cell division that result in formation of gametes (sex cells/ haploid cells)
A. Meiosis I
1. our cells have 2 sets of xsomes (1 set of 23 from mom, 1 set of 23 from dad)
2. each xsome in male set has a (**) xsome in the female set
3. (**)- same type of xsome contributed by each parent
4. Prophase I- replicated xsomes seek out their homolog and form a (**)
(**) occurs btwn homologs, exchange portions of their chromatids
5. Metaphase I- tetrads line up in the (**) of the cell
6. Anaphase I- spindle fibers separate (**) from each other.
7. Telophase I- nucleus reappears, cytokinesis, each cell has one of the homologs or
homologous chromosomes
B. Meiosis II- no more replication b/c it was already done during interphase
1. Metaphase II, Anaphase II, Telophase II
2. similar to (**), as cells go through another round of division
3. sister chromatids separate or (**), but in Meiosis I the homologs split
4. results in gametes or sex cells with a (**) number of xsomes
a. males- 1 cell = (**)
b. females- 1 cell = 1 egg or (**); unevenly divided so 1 egg gets most of the cytoplasm.
Remaining 3 cells are called polar bodies and usually don't participate in reproduction.
5. Meiosis produces (**) cells so that when a sperm & egg fuse during (**),
the (**) will have the same total number of chromosomes that each parent had
C. Contributors to Diversity in Organisms
1. Meiosis I- during prophase- (**) gives differrent combinations of genes than
before by mixing homologous chromosomes
2. Meiosis II, (**) of chromosomes into separate gametes
3. (**) can change survival or reproduction rates of species
a. (**)- expression that results in death
b. (**)- no effect on survival or reproduction
c. (**)- expression that results in survival advantages
II. Genes and types of Mutations
A. Genes
1. is a length of DNA located on (**).
2. there are (**) of genes on each xsome that encode information
3. gene expression is caused by controlling the sequence of a.a. in a (**)
4. genes are factors that control traits
5. (**)- genes on the same xsome
B. Gene Mutations
1. caused by a change in (**) sequence of a protein
2. impacts of mutations (**)
3. gene mutation- change to 1 or several bases in nucleotide sequence of DNA
a. bases added, deleted, replaced (changed)
i. (**)- single base or base pair change (Sickle Cell)
ii. (**)- 1 missing/added base, transcribed by mRNA
b. mutations are rare b/c cells have proofreading and correction (**)
c. these chance events (mutations) are caused by (**)
ex. viruses, UV light, chemicals like mustard gas
Deletion and addition Mutations animation
C. Chromosomal Mutations- change in structure or number of chromosomes
Detected by KARYOTYPING which matches homologous chromosomes in a diploid cell by:
1. size of chromosome
2. length of chromatid arms 3. centromere location
Samples are collected by doing either an amniocentesis or chorionic villus sampling.
Karyotype of a normal
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Karyotype of a normal
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fig 2.
C. Chromosomal Mutations Continued- change in structure or number of xsome
Theoretically Normal Chromos ome Structure
note : ea ch letter or seg men t o n a chro m oso me rep resen ts a gen e in pro per lo cus
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fig 3.
1. Structure (colored letters come from the fig 3. above)
a. (**) - loss of part of a xsome AC  DEF
b. (**) - segment is repeated ABBC  DEF
c. (**) - orientation is reverse of normal AED  CBF (twisting)
d. (**) - parts are broken off and added to another xsome
ex. ABC  DEF and GH  IJK is changed to ABC  JK and GH  IDEF
2. Nondisjunction deals with whole xsomes or sets of xsomes "not coming apart"
a. with one xsome- during meiosis cell gets both copies of a xsome and the other cell is
missing one xsome because sister chromatids didn’t separate
i. (**)- is the condition of having only 1 chromosome of a homologous pair,
Turner Syndrome= monosomy of 23rd pair
ii. (**)-is the condition of having 3 xsomes of a homologous pair,
Down Syndrome (21st pair), Klinefelter Synd (23rd pair)
b. (**)- extra sets of xsomes in the same cell
*animals die, but plants get larger
i. (**) (1N) - 1 set of xsomes, human gamete has 23 xsomes
ii. (**) (2N) - 2 sets of xsomes, human body cells have 46 xsomes
iii. (**) (3N) - three sets of xsomes
iv. (**) (4N) - four sets of xsomes
Using your skills, label the following karyotypes with the disorder (if any) and gender:
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fig 6.
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fig 9.