GENETIC PROCESSES Flashcards
Compare and contrast mitosis and meiosis (major similarities and differences)
ON EXAM
Mitosis
* Type of cell produced: Somatic
* Haploid or diploid: Diploid
* Where process occurs: Somatic cells
* Number of daughter cells produced: 2
* Unique or identical: Identical
Meiosis
* Type of cell produced: Sex
* Haploid or diploid: Haploid
* Where process occurs: Testes/ovaries
* Number of daughter cells produced: 4 sperm / 1 egg
* Unique or identical: Unique
Interphase
both cell growth and DNA replication occur in preparation for cell division
Prophase (pro = start)
- Chromatin strands become more tightly coiled. The strands join together and are now called chromosomes.
- Centrioles move to opposite ends/poles of the cell to give direction.
- Spindle fibers guide chromosomes and stretch across the cell from centriole to centriole.
- Nuclear membrane and nucleolus disappears
*
Metaphase (meta = middle)
Spindle fibers form
centrioles at opposite poles of the cell attach to the centromere of sister chromatids and move them to the equator (center line) of the cell
Anaphase (ana = backwards)
- Centromere splits apart and sister chromatids separate from each other
- Spindle fibers shorten and pull chromosomes to opposite poles of the cell
Telophase (telo = end)
- Chromosomes unwind and are once again called chromatin
- Spindle fibers breakdown, centrioles disappear
- Nuclear membrane reforms
- Nucleolus forms in each new nucleus
Cytokinesis
- Division of the cytoplasm to complete the process of making two new daughter cells.
Interphase I
- Chromosomes replicate
- Chromosome consists of 2 identical sister chromatids held together by a centromere
Prophase I
- Synapsis (chromosome fusion creates tetrads) happens here, homologous chromosomes align side by side.
- Crossing over also occurs and it is the exchange of genetic material between non-sister chromatids.
(crossing over)
Metaphase I
- Pairs of homologous chromosomes (homologues) line up at equator by independent assortment.
- Spindle fibres attach to centromeres.
(independent assortment)
Anaphase I
- Homologues separate, one of each pair going to each pole of the cell.
(nondisjunction)
Telophase I and Cytokinesis
- Two clusters of chromosomes have formed, each containing one member of each pair of homologues.
- Cytokinesis occurs.
- There is little or no interphase between meiosis I and meiosis II.
Prophase II
Sister chromatids condense, spindle fibers form
Metaphase II
- Sister chromatids line up along the metaphase plate.
- Spindle fibres attach at the centromere.
(independent assortment)
Anaphase II
Sister chromatids are pulled apart to opposite poles
(nondisjunction)
Telophase II and Cytokinesis
- Spindle fibers disappear, nuclear membranes reform, and cytokinesis occurs
- After cytokinesis, 4 unique daughter cells have formed, each with a haploid number (n) of chromosomes.
How many chromosomes do somatic cells have? How many chromosomes do gametes have?
Somatic cells (body cells) have 46 chromosomes, Gametes (reproduction cells) have 23 chromosomes
Genotype
- The combination of alleles for a trait. (eg. Rr)
- Letter code
Phenotype
The physical appearance of a trait. It is based on genotype.
Gene
sections of DNA that contain genetic information for the inheritance of specific traits.
Allele
Different forms of the same gene (e.g., different eye colors)
Dominant
The form of a trait that will always appear (be expressed)
(Eg. RR, or Rr)
Recessive
The form of a trait that will only appear (be expressed) if the individual has two alleles for it. (eg. rr)
Homozygous
- Describes the genotype of an individual with two alleles that are the same. (e.g RR or rr)
- RR= homozygous dominant
- rr= homozygous recessive
Heterozygous
Describes the genotype of an individual with two alleles for the same gene that are different. (eg. Rr is heterozygous dominant)
Codominance
a pattern of inheritance where both alleles are expressed at the same time.
Incomplete dominance
mix of both dominant traits are expressed (red + white = pink)
Homologous Chromosomes
paired chromosomes similar in size and gene arrangement, but different alleles.
Be able to complete basic monohybrid and dihybrid crosses (punnett squares) and determine the probability/ratio of offspring (genotype and phenotype)
- Monohybrid cross ratio: 3 to 1 (3:1)
- Dihybrid cross ratio: 9 to 3 to 3 to 1 (9:3:3:1)
Nondisjunction
- failure of one or more pairs of homologous chromosomes or sister chromatids to separate normally
- the result will be an embryo with extra or fewer chromosomes
Trisomy
- Trisomy: Inheriting one extra chromosome can result in various syndromes such as..
- Trisomy 21- Down Syndrome
- Trisomy 18- Edwards syndrome
- Trisomy 13- Patau’s syndrome
- XXY - Klinefleters
- XYY- Jacobs
- XXX- Triple X syndrome
Monosomy
- Monosomy: inheriting one less chromosome, for example
- XO- Turners
universal donor
O universal donor: no antigens to react with other bloods antibodies
Universal recipient
AB Universal recipient: universal donor because it contains no antibodies to react with other bloods antigens
can a person with Type A blood receive Type B blood? Why or why not?
A and B blood cannot mix: A blood has B antibodies and B blood has A antibodies, when the antigen meets the antibody it can cause blood clotting and arterial resistance which can lead to cardiac arrest, stroke, and high blood pressure.
