Unit 5 - Heredity Flashcards
common ancestry
- DNA and RNA carry genetic info
- genetic code is shared by all living systems
- Gregor Mendel studied inheritance and created two laws that can be applied to the study of genetics
genetics
study of heredity and hereditary variation
heredity
transmission of traits from one generation to the next
traits are passes from parent to offspring through…
genes
asexual reproduction
- single individual
- no gamete fusion
- clones
- mutations are only source of variation
- can produce asexually through mitosis
- advantage: quick & easy
sexual reproduction
- 2 parents
- offspring are unique combinations of genes
- genetically varied from family
- the less related you are to your partner, the smaller the chance for genetic disorder
- disadvantage: takes longer
homologous chromosomes
pair of chromosomes that carry same genetic information (inherited one from mom/dad)
karyotypes
display of chromosome pairs ordered by size and length
somatic cells
- body cells
- diploid (2n)
- 2 complete sets of each chromosome
gametic cells
- sex cells
- haploid (n)
- one set of each chromosome
eukaryotes
have DNA that is packaged in chromosomes
autosomes
chromosomes that do not determine sex
sex chromosomes
X and Y
23rd chromosome pair
eggs
X
sperm
X or Y
life cycle
sequence of stages in reproductive history of an organism form conception to its own conception
fertilization and meiosis…
alternate in sexual life cycles
fertilization
sperm cell (haploid) fuses with an egg (haploid) to form a zygote (diploid)
all sexually reproducing organisms have
both a diploid and a haploid number
meiosis
process that creates haploid gamete cells in sexually reproducing diploid organisms
meiosis results in daughter cells with…
half the number of chromosomes as the parent cell
mitosis
- occurs in somatic cells
- 1 division
- results in 2 diploid daughter cells
- daughter cells are genetically identical
meiosis
- forms gametes (sperm/egg)
- 2 divisions
- results in 4 haploid daughter cells
- each daughter cell is genetically unique
three key events of meiosis
prophase I, metaphase I, anaphase I
prophase I
- synapsis and crossing over
- crossing over (recombination) occurs at the chiasmata and DNA is exchanged between the homologous pairs
- every chromatid that is produced has a unique combination of DNA
metaphase I
independent orientation: tetrads (homologous pairs) line up at metaphase plate
anaphase I
homologous pairs separate
interphase
cell goes through G1, S, G2
synapsis
homologous chromosomes pair up and physically connect to each other forming a tetrad
anaphase I
- pairs of homologous chromosomes separate
- sister chromatids are still attached
telophase I and cytokinesis
- nuclei and cytoplasm divide
- there is now a haploid set of chromosomes in each daughter cell
prophase II
- no crossing over
- spindle forms
metaphase II
- chromosomes line up at the metaphase plate
- because of crossing over in meiosis I, the chromatids are unique
anaphase II
sister chromatids separate and move towards opposite poles
telophase II and cytokinesis
- 4 haploid cells
- nuclei reappear
- each daughter cell is genetically unique
early meiosis I
parent cell: 2n = 4
end of telophase II and cytokinesis
each daughter cell: n = 2
how does meiosis lead to genetic variation
- crossing over
- independent assortment of chromosomes
crossing over
