what is the animal life cycle and reproduction?
Key Terms
what is the animal life cycle and reproduction?
what is the plant life cycle and reproduction?
Answer: sporophyte (2n) –> meiosis –> spore (n) –> gametophyte (n) –> female gamete or male gamete (n) –> fusion –> zygote (2n) –...
explain meiosis
Answer: > produces haploid gametes - sperm or egg cells one round of DNA duplication in a diploid cell (s phase) - as for mitosis two cell divis...
describe the process of meiosis
Answer: meiosis I > first division - reduces chromosome # from diploid to haploid - by separating homologous chromosomes Meiosis II >second d...
how does sex contribute to genetic variation?
Answer: > homologous chromosomes segregate and the non-homologous chromosomes assort independently during gamete formation, this creates differe...
what is independent assortment of alleles?
Answer: > variants of the same gene (i.e., alleles) account for trait variation variation between individuals results from different combination...
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| Term | Definition |
|---|---|
what is the animal life cycle and reproduction? | Answer: adult (2n) –> meiosis –> egg or sperm (n) –> fusion –> zygote (2n) –>mitosis –> adult |
what is the plant life cycle and reproduction? | Answer: sporophyte (2n) –> meiosis –> spore (n) –> gametophyte (n) –> female gamete or male gamete (n) –> fusion –> zygote (2n) –> mitosis –> sporophyte. |
explain meiosis | Answer: > produces haploid gametes - sperm or egg cells one round of DNA duplication in a diploid cell (s phase) - as for mitosis two cell divisions - i. reduction division (haploid) - ii. separation of chromatids (haploid) |
describe the process of meiosis | Answer: meiosis I > first division - reduces chromosome # from diploid to haploid - by separating homologous chromosomes Meiosis II >second division - separates chromatids - four haploid gametes per starting cell. |
how does sex contribute to genetic variation? | Answer: > homologous chromosomes segregate and the non-homologous chromosomes assort independently during gamete formation, this creates different outcomes. in humans: 2^23 = ~ 8 million unique gametes from one individual |
what is independent assortment of alleles? | Answer: > variants of the same gene (i.e., alleles) account for trait variation variation between individuals results from different combinations of alleles ~4^10,000 possible unique gametes! |
Explain gentic variation via recombination | Answer: > recombination events (crossovers) occur at pachytene (a stage in prophase I of meiosis I) at different sites along the chromosomes. Some sites, so-called “hotspots” are used more often than other sites. mixes paternal and maternal regions between homologous chromosomes gives rise to new combinations of alleles on a chromosome. point of crossing over is called a chiasma |
what are the four main sources of variation in cells? | Answer: > mutations - new alleles independent assortment of homologous chromosome pairs (in meiosis) - different combinations of parental chromosomes in different gametes recombination (crossing over in meiosis I) - new combinations of alleles on chromosomes fusion of gametes (in fertilisation) |
What happens when meiosis goes wrong | Answer: > non -disjunction of homologous chromosomes in meiosis I or sister chromatids in meiosis II chromosomes sometimes fail to separate properly during meiosis I or II gametes +/- chromosome zygote will be aneuploid (often lethal) (2n +/- 1) e.g, down syndrome, trisomic chromosome 21 ( 47, +21) |