Meiosis Flashcards
Heredity
The passing of genes from one generation to the next
Trait
A genetically determined characteristics
Genetics
The study of heredity and heredity variation
Locus
A gene’s specific location on a chromosome
Somatic cells and how many chromosomes humans have?
Normal cells in an organism
Have 46 chromosome
Gametes
Reproductive cells that pass genes(DNA) from generation to another
Gene
If it inherited and causes a trait (phenotype), it’s a gene
Asexual Reproduction
Parent is a single individual
**All cells are made by mitosis - all cells are genetically identical
The descendants (progeny) are genetically identical to the parents(clone)
Pros and Cons of Asexual reproduction
Pros: Fast
less genetic expensive
Cons: Less genetic diversity in the population
Sexual Reproduction
Two parents
**Gametes are made meiosis - gametes are not genetically identical to parent
Descendants are NOT genetical to parent
Pros and Cons of Sexual Reproduction
Pros: More genetic diversity in population which can withstand environmental changes
much wider variety of phenotypes
Cons: Need to find a mate(energetically more expensive)
Life Cycle
The series of stages in the reproductive history of an organism(from conception to production of its own offspring)
Diploid
These are cells that contain two copies of each chromosome(46)
There are 23 pairs of chromosomes. True/ False
True.
Humans have 22 pairs of autosomal chromosomes and 1 pair of sex chromosomes (X and Y). True/ False
True.
Homologous Chromosomes
Two chromosomes in a pair
Alleles
These are genes, one from mother and one from father
Haploid
Only one chromosome(23) in each cell(Gametes)
Fertilization
Merging of two haploid gametes to form diploid zygote
Sporophyte
Spore producing phase(asexual phase) and diploid phase
Gametophyte
Haploid Phase or sexual phase
Ploidy
The number of sets of chromosomes in a cell. **Humans somatic cells are diploid(2n)
Identical twins have the same combination of alleles. True/False
True
Chromosomes are counted by the number of centromeres. True/False
True
What are the sources of genetic variation
Crossing Over(homologous recombination) in prophase 1
Independent Assortment of homologous (various combinations of maternal and paternal chromosomes) chromosomes at metaphase/anaphase 1
Random fertilization(not in meiosis but part of process)
Recombinant Chromosomes/Cross over
The swapped sections of DNA between non-sister chromosomes.
Cohesins
Hold sister chromatids together
Recombination happens during the raveled stage of the chromosome (euchromatin). True/False
True
Steps to Recombination
DNA strand breaks are made by proteins on non-sister chromatids
Synaptonemal complex hold non-sister chromatids together
Crossing over occurs
Recombination occurs on both sets of non0-sister chromatids
Synaptonemal Complex
are proteins that hold the non-sister chromatids together
Chiasmata
These are regions where non-sister chromatids have swapped(crossovers occurred)
Synapsis
The close fusion of homologous chromosomes
The chromosomes are fully condensed at the end of interphase. True/False
False. The chromosomes are fully condensed at the end of prophase 1
Prophase 1
Nuclear Envelope breakdown
Mitotic spindle forms along with centrosome movement
Crossover and recombination occurs (earlier prophase)
Metaphase 1
Duplicated homologous chromosomes are aligned at the metaphase plate (this is random)
microtubules attached to one pair of sister chromatids
Anaphase 1
**Centromeres that hold homologous proteins together detach
**Homologous chromosomes separate
Cohesin proteins remain together
kinetochore stays together
Telophase 1 and Cytokinines
Each nucleus has a haploid set of duplicated chromosomes
Each chromosome is a sister chromatids
No duplication occurs before going into the next stage
Prophase 2
Similar to prophase 1
Nuclear envelope breaks down, mitotic spindle forms, centrosomes move to the ends of the cell
Metaphase 2
chromosomes are aligned at metaphase plate
Sister chromatids attached by kinetochores to a microtubule
Because of crossing over the sister chromatids are not identical
Anaphase 2
Cohesins are broken down. Chromososmes are moved to opposite poles
Telophase 2 and Cytokinesis 2
nuclei form, chromosomes decondense
each cell has haploid
haploid daughter cells form
autosomal and sex chromosome cross over. True/False
False. Only autosomal chromosomes cross over