The Physical Basis Of Heredity Flashcards
Where is the “heredity” factor?
In the nucleus
Do chromosomes occur in pairs?
Yes
When do chromosomes separate?
At meiosis
How do members of chromosome pair appear to segregate?
Independently
Most animals have what kind of cells?
Diploid
Diploid
2n or two sets (one pair) of chromosomes
Autosome
Pairs 1-22 the “not sex chromosomes”
What is the last pair of chromosomes?
Sex chromosomes
XX
Female
XY
Males
Homologous chromosomes
Paired corresponding chromosomes
What are homologous chromosomes similar in?
In morphology, centromere position, and the genes that each carry
Centromere
The largest constriction site on the chromosome
What is the site of spindle fiber attachment during mitosis?
The centromere
How many chromatids per centromere?
2
Sister chromatids
The two chromatids that make up one chromosomes
Telomere
Tips of the chromosome
How do you describe chromosomes?
By centromere position
Telocentric
Centromere at tip
Acrocentric
Centromere close to tip
Submetacentric
Centromere off center
Metacentric
Centromere at middle
Karyotype
A chart arranging chromosome pictures according to their size, grouped by pairs of homologs
How are chromosomes numbered in Karyotypes?
In order of size and centromere position
Ideogram
A schematic representation of a chromosome
Shorter arm in ideogram
P arm
Longer arm in ideogram
Q arm
How are major banding regions in ideograms indicated?
With numbers
Microsomes
artificial structures derived from pieces of endoplasmic reticulum (ER) formed during tissue homogenization
Cytogenetic
Genetic sub discipline that focuses on chromosome variations
What can abnormal gene or chromosome copy numbers lead to?
Genetic abnormalities
When are chromosomes visible (this is the time we Karyotype)?
During metaphase when the chromatids are lined up
What is chromatin made of?
DNA and protein
Chromatin
the material of which the chromosomes of organisms other than bacteria (i.e., eukaryotes) are composed. It consists of protein, RNA, and DNA.
Where is chromatin located?
Outside of of nucleolus
Cell Cycle
G1 —> S —> G2 —> Mitosis
What two steps make up interphase?
G1 and S
G1 Phase
Time cell growth before DNA is copied (chromosomes unduplicated)
S Phase
Time of cell growth when the DNA is copied (all chromosomes duplicated)
G2 Phase
Time after DNA replication the cell prepares to divide
What are the four phases of mitosis?
- Prophase
- Metaphase
- Anaphase
- Telophase
Prophase
When microtubules attach to the centromeres of the sister chromatids
Metaphase
Spindle fibers line up chromosomes in the middle
Aster
Where spindle fibers come out from
Anaphase
Spindle fibers begin pulling sister chromatids apart
Telophase and cytokinesis
Sister chromatids are separated and cleavage furrow and nucleus/nuclear envelope begin to form
When does cytokinesis begin?
Towards the end of anaphase
When does cytokinesis end?
Finishes after telophase
What happens during cytokinesis?
-Cleavage furrow forms
-microfilaments pull plasma membrane inward around the cell
-pinches the cell in two
Daughter cells are _____.
2n
What is the function of mitosis?
Growth, including repair and maintenance
Where does mitosis occur in?
Somatic/body cells
What is the mechanism of mitosis?
Chromosomes are duplicated once then cytoplasm is divided
What is the outcome of mitosis?
Maintains the diploid chromosomes number 2n —> 2n
Effect of mitosis
Two diploid daughter cells
Function of meiosis
Gamete production (sperm/eggs)
Where does meiosis occur at?
Germ cells in gonads (testes/ovaries)
Mechanism of meiosis
Chromosomes are duplicated twice then the cytoplasm is divided
Outcome of meiosis
Halves the diploid chromosome number 2n—>n
Effect of meiosis
Four haploid daughter cells
What is meiosis?
Single DNA replication two division of the cytoplasm
What happens during meiosis I?
- separation of homologs
-reduces chromosomes to haploid
What happens during meiosis II?
Equational division; sister chromatids of haploid cells are separated
Genetic recombination
As chromosomes move closer together synapsis occurs and chromatids break and exchange genetic information
What species can you cross?
Species with the similar chromosome numbers
Why are mules infertile?
Because a horse has 64 chromosomes and a donkey has 62 so when a mule is born it has 63.5 and cannot reproduce with other mules
Why can ligers or tigons reproduce but not mules?
Because most cats have the same chromosome number so hybrids will have the same as well and can reproduce