Chapter 7: Patterns of Chromosome Inheritance Flashcards
Chromosome
The structure that contains genetic information (DNA) and allows for transfer from one generation to the next
Sections of DNA that code for specific what?
Proteins = genes
DNA + proteins that assist in
Organizational structure = chromatin
Human have
46 chromosomes
23 pairs of homologous chromosomes
1 copy from each parent
This makes us
Diploid (2 sets) not haploid (1 set)
Sister chromatids
In dividing cells, each chromosome has two sister chromatids connected at the centromere.
The cell cycle: Cell growth is regulated by
The cell cycle, divided into dividing and non-dividing (interphase) sections
Gap 1: Cell does
Its job, by growing and prepares
DNA synthesis (S-phase)
Copies of chromosomes are made
Gap 2: Further prep for
Cell division, including growth and checking DNA copies for errors
Mitosis
The general form of replication (growth, replacement)
Mitosis does not require genetic input from
Another organism, thus asexual
Step of mitosis
1) Prophase
2) Metaphase
3) Anaphase
4) Telophase
5) Cytokinesis
Prophase
Chromosomes condense, nuclear envelope degrades
Metaphase
Sister chromatids line up along the center of the cell
Anaphase
Sister chromatids pairs separate pulled to opposite poles in the cell
Telophase
Chromosomes uncoil, the new nucleus forms, cleavage into two daughter cells
Cytokinesis
Splitting up of cytoplasm, replicating of organelles, final separation
Meiosis
Specialized type of cell division only for sexual reproduction and only found in diploid organisms
Two keys differences from mitosis
1) Meiosis reduces the genetic material found in daughter cells
2) Produces cells that are different from each other (allelic variations)
Steps of meiosis
1) Prophase 1
2) Metaphase 1
3) Anaphase 1
4) Telophase 1
Prophase 1
Chromosomes condense, nuclear envelope degrades, crossing over occurs
Metaphase 1
Chromosomes line up along the center of the cell
Anaphase 1
Homologous chromosomes separate, pulled to opposite poles in the cell
Telophase 1
Chromatids form the new nucleus, cells separate, cytokinesis occurs
Note the difference from mitosis
1) In mitosis: 2 identical daughter cells produced
2) In meiosis: 2 different, haploid daughter cells produced
Steps of meiosis (Continued)
1) Prophase 2
2) Metaphase 2
3) Anaphase 2
4) Telophase 2
Prophase 2
Chromosomes recondense
Metaphase 2
Sister chromatids line up along the center of the cell
Anaphase 2
Sister chromatids pulled to opposite poles of the cells
Telophase 2
Chromosome uncoil, new nucleus forms, cytokinesis occurs
Result of meiosis
Get 4 unique, haploid cells from 1 diploid cell
These unique haploid cells are
Gametes (sex cells, sperm/eggs)
Meiosis only occurs in the
Gonads, and is only for sexual reproduction
In humans, there are
46 chromosomes total
Because we are diploid organisms, there are
23 homologous pairs
Each sperm or egg contains
23 chromosomes
Female gametes are
Bigger than male gametes
Male gametes tend to be
Motile have very little cytoplasm, and produce 4 equal daughter cells via meiosis
Female gametes tend to be
Non-motile, with cytoplasm and divide unevenly to produce only one viable daughter cell via meiosis
Why sexual reproduction?
1) Asexual reproduction
2) Sexual reproduction
3) Variability
Asexual reproduction
More efficient, it allows parental DNA to be directly carried to the next generation (removing the risk of not finding a mate)
Sexual reproduction
High variability
1) Crossing over creates unique allelic combinations
2) Shuffling of homologous adds variability
3) Fertilization (mixing of 2 individuals to create 1)
Variability
Adaptation to change (beneficial for survival in a changing environment)
Sex determination one of the 23 chromosomes in humans determines gender (male or female)
Female: XX (homozygous)
Male: XY (heterozygous)
How do we know that no essential genetic information is
Carried on the Y chromosome
In birds, heterozygous individuals are
Female
Female is not
Default in all species
In many insect species,
1) Haploid: Male
2) Diploid: Female
In reptiles, the mother selects the sex of
Offspring by regulating nest temperature
Chromosomal Irregularities
Nondisjunction
Nondisjunction
Unbalanced division during meiosis causes polyploidy (more than 2 copies of a chromosome) or missing chromosomes
Nondisjunction
1) Not necessarily fatal
2) Common in plants
3) In humans, extra copy of chromosome 21 causes Down syndrome
Sex chromosome issues
In human
X-Turner syndrome
Express as underdeveloped females, typically sterile
XXY-Klinefelter syndrome
Rarely diagnosed; requires reproductive assistance
XYY-Jacobs syndrome
Very tall, acne-prone, speech/reading problems
XXX Poly-X females
Normal appearance, motor, language delays possible
