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vinh do

bio test 3 chapter 11

QuestionAnswer
Sexual reproduction is the production of offspring through the union of gametes. What are gametes? Eggs and sperm
Sexual reproduction depends on ?, which is a specialized process of ? meiosis, cell division that produces gametes
It is important that meiosis occurs because gametes must have ? present in the ? half the number of chromosomes, somatic cells (body cells)
what generates the variability that is the basis of most inherited differences? Sexual reproduction
In humans, meiosis occurs in the gonads
The male gonads are the ?, that produce ? testes, spermatozoa (sperm)
The female gonads are the ?, that produce ? ovaries, ova (eggs)
Meiosis will separate the homologous pairs, reducing the ? number of chromosomes to ?. diploid, haploid
Each gamete produced by meiosis receives the ? member of each homologous pair
Humans have how many chromosomes altogether? 46
So after meiosis, eggs/sperms will have how many chromosomes? 23
the diploid chromosome number will be restored during what? fertilization
Meiosis is a two-part process of cell division. It is broken down into: meiosis 1 meiosis 2
During meiosis I separates the homologs, placing one in each of the two cells
During meiosis II sister chromatids separate into four different cells
Prophase I sister chromatids condense; the two chromosomes of each homologous pair undergo pairing (synapsis), forming tetrads; chromatids of homologous chromosomes physically exchange segments (crossing-over)
Prometaphase I nuclear envelope breaks down; the spindle enters the former nuclear area and attaches to the kinetochores
Metaphase I tetrads line up at the metaphase plate
Anaphase I two chromosomes of each homologous pair separate; each chromosome still has two sister chromatids
Telophase I little or no change in the chromosomes
Interkinesis spindle of the first meiotic division disassembles
Prophase II spindle microtubules forms
Prometaphase II spindle microtubules attach to the kinetochores of each chromosome
Metaphase II spindle microtubules align chromosomes on the metaphase plate
Anaphase II spindles separate the sister chromatids
Telophase II chromosomes decondense; spindles disassemble, new nuclear envelopes form around the chromatin; result is four haploid cells
What happens during a nondisjunction? The spindle fails to separate the homologous chromosomes (in meiosis I) or the sister chromatids (in meiosis II)
Sex chromosomes are pairs of chromosomes that are different in males and females of the same species.
Females sex chromosome will have Males will have XX, XY
Genetic variability is the main evolutionary advantage of sexual reproduction. How is this so? Variability increases the chance that at least some offspring will survive and reproduce in changing environments
During meiosis, genetic variability arises from three sources 1. genetic recombination 2. random segregation 3. random fertilization
Genetic recombination is also known as ? This process occurs during ? of meiosis. crossing-over, prophase I
What is random segregation? When does this process happen? One of each homologous pair is randomly placed on either side of the metaphase plate; random during metaphase I
What are the total possible combinations in humans? 8 million possible combinations of chromosomes at the metaphase plate
What are the chances of having two children with the exact same combination of chromosomes? Why is this number so high? 1 out of trillion at puberty, a female will have about 300,00 eggs a male produces millions of sperms at a time
Created by: 752247243
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