Quiz 4 Flashcards
genetics
scientific study of heredity and variation
heredity
transmission of traits from one generation to the next
variation
differences in appearance of offspring from parents and siblings
how are traits inherited?
through genes, specific sites on chromosomes
- physical characteristics (like big muscles) not inherited
what are genes and how are they passed on
units of heredity; made up of segments of DNA packaged into chromosomes
- each has a specific location on a chromosome (locus)
- passed on to the next generation via reproductive cells called gametes (sperm and egg)
asexual reproduction and its benefits
mitosis - single individual passes genes to offspring without fusion of gametes
*good in times of environmental uncertainty!
clone
group of genetically identical individuals from the same parent (created via mitosis)
sexual reproduction
meiosis - two parents give rise to offspring with unique combinations of genes (from both parents) through the fusion of gametes
exceptions to rules of asexual/sexual reproduction
some protists reproduce “sexually” without sperm/egg gametes
homologous chromosomes and how many do humans have
the 2 chromosomes in each pair; one from mother and one from father
- same length/shape and carry genes controlling the same inherited characteristics
- humans have 23 pairs of chromosomes; females have 23 homologous pairs and males have 22 homologous pairs
karyotype
ordered display of pairs of chromosomes from a cell
sex chromosomes
determine biological sex of an individual
- females are homologous (XX)
- males are XY (Y is shorter, may have broken off ancestral X)
autosomes
remaining 22 pairs of chromosomes in humans
what happens to homologous chromosomes during DNA replication?
each chromosome is replicated and each replicated chromosome makes 2 identical sister chromatids
*4 chromatids for a homologous pair
what are haploid cells and where are they produced in humans
haploid cells: single set of chromosomes
- gametes (sperm or egg) are human haploid cells (haploid number: 23)
- gametes produced by cells in gonads (testes and ovaries) that undergo meiosis
how do organisms maintain chromosome number?
fertilization and meiosis alternate in organisms with sexual life cycles
- 3 main types
life cycle
generation-to-generation sequence of stages in the reproductive history of an organism
- in organisms with sexual life cycles, fertilization and meiosis alternate to maintain chromosome #
- 3 main methods of alternation
life cycles in animals
- gametes are only haploid cells; undergo no further division before fertilization
- gametes fuse during fertilization to become a diploid zygote
- zygote divides by mitosis to form a multicellular organism
life cycles in plants/some algae
includes both diploid and haploid multicellular stage!
- diploid sporophyte makes haploid spores by meiosis
- spores grow by mitosis to form a haploid gametophyte
- gametophyte makes haploid gametes by mitosis
- fertilization of 2 gametes results in a diploid sporophyte
life cycles in fungi/some protists
- only diploid stage is the single-celled zygote
- zygote produces haploid cells by meiosis
- haploid cells grow by mitosis to form multicellular organisms
- haploid adults produce gametes by mitosis that fuse to create diploid zygotes
which types of cells can undergo mitosis/meiosis?
- all cells can divide by mitosis
- only diploid cells can divide by meiosis