Meiosis I

Question 1

what is a trait?

Answer 1

a trait is a variation of a character. for example: black hair, brown hair, blue eyes. character is: eye color, hair color.

Question 2

how do we get the traits we do from our parents?

Answer 2

we get the coded information for these traits on hereditary units called genes.

Question 3

what is a gene?

Answer 3

a gene is a segment of a chromosome that directs the synthesis of a functional product.

Question 4

what is a locus?

Answer 4

the position of a gene along a chromosome is called a locus

Question 5

genes are transmitted to offspring in plants and animals by?

Answer 5

sexual reproduction

Question 6

the offspring is a __ of?

Answer 6

mixture of the genes inherited from mother and father.

Question 7

what is asexual reproduction

Answer 7

offspring is produced by a single parent. all of the genetic information is transmitted.

Question 8

what organisms reproduce asexually?

Answer 8

• prokaryotes
• single celled eukaryotes: amoeba
• some multicellular organisms: hydra

Question 9

how many chromosomes do somatic cells have?

Answer 9

46 chromosomes, 2 sets of 23 each

Question 10

human somatic cells are?

Answer 10

diploid: two copies of each chromosome. homologous chromosomes. (the two copies of chromosome 1 in a cell would be homologous chromosome)

Question 11

of the 46 chromosomes in a human somatic cell?

Answer 11

22 pairs of non sex chromosomes and the remaining two chromosomes are sex chromosomes.

Question 12

what are non sex chromosomes called?

Answer 12

autosomes

Question 13

what are the two sex chromosomes and what is the difference for male and female?

Answer 13

two sex chromosomes are x and y
- male: xy
- female: xx

Question 14

if you are female you have?

Answer 14

44 autosomes and 2 x chromosomes
- one set from mother: 22 autosomes and x
- one set from father: 22 autosomes and x

Question 15

if you are a male you have?

Answer 15

44 autosomes and xy chromosomes.
- one set from mother: 22 autosomes and x
- one set from father: 22 autosomes and y

Question 16

normal karyotype for male/female?

Answer 16

female: 46 in total with 2 x
male: 46 in total with xy

Question 17

somatic cells undergo?

Answer 17

the cell cycle which includes mitosis and cytokinesis

Question 18

cells replicate their chromosomes during the?

Answer 18

cell cycle

Question 19

after replication, the chromosomes?

Answer 19

remain joined together at the centromere.

Question 20

at this point, they are referred to as?

Answer 20

sister chromatids

Question 21

human somatic cells contain 46 chromosomes, how many do sex cells contain?

Answer 21

sex cells/gametes/sperm or egg cells: contain 23 chromosomes only

Question 22

a cell that has one copy of each chromosome is?

Answer 22

haploid.

Question 23

the human life cycle begins when?

Answer 23

ovum and sperm fuse together to form a zygote.

Question 24

the zygote is haploid or diploid?

Answer 24

the zygote is diploid because there is a maternal set and a paternal set: 2 sets

Question 25

all somatic cells in the human are derived by?

Answer 25

mitotic division of the zygote.

Question 26

the gametes: sperm and ovum are derived by?

Answer 26

meiosis

Question 27

where does meiosis occur?

Answer 27

meiosis occurs in the gonads

Question 28

what are the gonads?

Answer 28

ovaries in females and testes in males

Question 29

meiosis acts to?

Answer 29

half the number of chromosomes

Question 30

the gametes will have how many chromosomes?

Answer 30

23 chromosomes

Question 31

meiosis consists of?

Answer 31

2 cell divisions: meiosis i and meiosis ii.

Question 32

before undergoing meiosis cells...?

Answer 32

replicate their chromosomes in the s phase of the cell cycle.

Question 33

prior to meiosis, all ?

Answer 33

46 chromosomes have replicated

Question 34

what are the stages in meiosis i and ii

Answer 34

pmat i and ii

Question 35

what happens in prophase i?

Answer 35

-nuclear envelope disintegrates - spindle apparatus forms - centrosomes move away from eachother - homologous chromosomes come together : synapsis: leading to the formation of tetrads. - the homologous chromosomes cross over and exchange dna - this leads to recombinant chromosome formation - each chromosome then has a mixture of genes derived from two parents

Question 36

what is the chiasmata?

Answer 36

regions where crossing over has occurred.

Question 37

what happens in metaphase i?

Answer 37

the tetrads move to the metaphase plate by the spindle fibers from centrosomes. this movement is random: independent assortment

Question 38

what happens in anaphase i?

Answer 38

- homologous chromosomes separate and move to opposite ends of the cell.

Question 39

what happens in telophase i/cytokinesis?

Answer 39

the homologous chromosomes are at opposite ends. the cell then divides by cytokinesis

Question 40

at the end of meiosis i, how many cells are formed?

Answer 40

2 cells are formed

Question 41

are the cells formed diploid or haploid?

Answer 41

the cells formed are haploid, they each have one copy of each chromosome, the sister chromatids are still together.