Ch 13 Flashcards
Heredity
Inheritance, transmission of traits
Genetics
Study of heredity and hereditary variation
Genes
Hereditary units with coded information on chromosomes
Locus
Location of gene on chromosome
Gametes
Reproductive cells with n chromosomes
Somatic cells
All body cells other than gametes with 2n chromosomes
Describe the relationship between genes and chromosomes
One chromosome contains several hundred to a few thousand genes
Asexual reproduction
Individual is the sole parent and passes copies of all of its chromosomes to its offspring. No fusion of gametes.
Clone
Group of genetically identical individuals
Asexual reproduction benefit vs drawback
Fast
No variation and therefore less likely to survive
Sexual reproduction
Two parents give rise to offspring that have unique combinations of genes inherited from the two parents
Effect of sexual reproduction
Genetic variation
Define life cycle
Generation to generation sequence of stages in the reproductive history of an organism. Conception to production of its own offspring.
Homologous chromosomes other name
Homologs
Homologous chromosomes
The two chromosomes composing a pair. Same length, centromere position, and gene locations.
Exception to Homologous chromosomes
Pair of male sex chromosomes
Karyotype
Ordered display of chromosomes starting with the longest
What would the human karyotype look like?
23 pairs totaling 46 chromosomes. 1-22 and x and y
Sex chromosomes
X and y, determine an individual’s sex
Autosomes
The others that aren’t sex chromosomes
Haploid
Single set of chromosomes
Diploid
Two sets of chromosomes
What stage of the life cycle is haploid?
gametes (sperm and egg)
What stage of the life cycle is diploid?
zygote into adulthood
What life cycle process converts from haploid to diploid
fertilization
What is fertilization?
union of gametes and fusion of their nuclei
What life cycle process converts from diploid to haploid?
meiosis
alternation of generation
life cycle that includes both diploid and haploid stages that are multicellular
What organisms exhibit alternation of generation?
plants and certain algal species
sporophyte
multicellular diploid stage
gametophyte
multicellular haploid stage
Two important stages of prophase I
synapsis and crossing over
synapsis
the pairing of homologs along lengths
crossing over
genetic rearrangement between non sister chromatids
chiasmata
x-shaped regions where a crossover has occurred
What is the name of the zipper-like protein structure in synapsis?
synaptonemal complex
Meiosis is broken down into
meiosis I and II
Similarities between meiosis I and II
same stages to produce daughter cells, similar splitting of DNA
Differences between meiosis I and II
duplication only before I, produces diploid in I vs. haploid in II, separates chromosomes in I and chromatids in II.
What events produce genetic variation?
meiosis and fertilization
How do meiosis and fertilization produce variation?
- independent assortment/random orientation of chromosomes
- Crossing over: recombinant chromosomes that aren’t exclusively maternal or paternal
- Random fertilization
