meiosis (everything test) Flashcards
Genotype
Composed of 2 alleles and represents the makeup of the gene. (ex: TT, Tt, tt)
Phenotype
The physical trait expressed due to a genotype (ex: tall, short)
Homologous pair
Chromosomes that are the same size, shape, and contain genes for the same trait
Describe how spermatogenesis occurs. How many total cells are produced?
be very specific
- making sperm from a male primary sex cell
- results in 4 genetically unique sperm
Synapsis
where does it occur? be specific
- is the process during meiosis in which homologous chromosomes pair up and align closely with each other
- occurs in prophase 1
Crossing over and where it occurs
be specific
- occurs at the beginning of meiosis 1 (prophase 1)
- homologous chromosomes get so close that they twist and exchange random segments
Disjunction and non-disjunction
- disjunction is the normal process of chromosome separation that occurs during meiosis.
- results in accurate genetic inheritance
- nondisjunction occurs when chromosomes fail to separate properly during meiosis (meiosis 1 and 2)
- results in an abnormal chromosome distribution and health consequences
Describe how oogenesis occurs. What is an oocyte? How many total cells are produced?
- making oocytes from a primary sex cell
- oocyte: immature reproductive (germ) cell that will mature into an ovum (egg)
- results in 1 ovum and 3 polar bodies
What are polar bodies and why do they not survive?
cells with too little cytoplasm to survive. (cytoplasm provides nutrients for the zygote)
Three factors that contribute to genetic variation?
- crossing over (during)
- independent assortment (during)
- random fertilization (after)
When does crossing over occur?
prophase 1
Describe independent assortment and how it contributes to genetic variation.
- occurs during metaphase, influencing anaphase
- completely random how the chromosomes line down the equator of the cell in metaphase before they separate during anaphase
- independent assortment increases diversity and random combinations
Describe random fertilization and how it contributes to genetic variation.
- random as to which sperm fertilizes the ovum
- increases genetic diversity and mixing genetic material
What type of cell must a mutation occur in to be passed on to the next generation?
germ cell
Causes, effects, and types of mutations
- changes in the DNA sequence that can occur in various ways
- include insertions/deletions, inversions, duplications, etc
- can have neutral, beneficial, harmful, or lethal effects, depending on the circumstances
Why is disjunction necessary for daughter cells to receive the correct number of chromosomes
- ensures equal distribution of chromosomes
- ensures chromosome number across generations (and correct number of chromosomes)
What results in nondisjunction? What sort of disorders result form it?
- when chromosomes fail to separate properly
- nondisjunction comes from problems with spindle fiber attachment, failure of chromosomes to separate, and chromosome alignment errors
- it can result in down syndrome, turner syndrome, etc
What happens in Meiosis 1 and Meiosis 2? What are the products? What cells are produced from Meiosis?
remember where the chromsomes become single or double
- Meiosis 1: reduces the number of chromosomes from 2n to n and produces 2 cells with half the number of double stranded chromosomes of the parent cell
- Meiosis 2: similar to mitosis, the 2 resulting cells from meiosis 1 then create 2 more cells with single stranded chromosomes
- starts with 1 diploid cell and results in 4 haploid cells (unidentical)
Gene
Segment of DNA that codes for a trait (protein) such as skin color
