meiosis / sexual

Question 1

Meiosis & crossing over

Answer 1

Process in which the number of chromosomes in the gametes are reduced by half

Gamete = sperm/egg cell
2n - diploid (46)
N - haploid (23)

Question 2

Chromosomes

Answer 2

Occur in similar pairs called homologous

One chromosome from the pair comes from each parent

Human cells have 46, making up 23 pairs of homologous chromosomes

Chromosomes of a homologous pair, carry genes for the same characteristics at the same place

Each version is referred to as an allele

Question 3

Prophase 1

Answer 3

Homologous pairs match up and become attached at their centromeres

Pairing process is called synapsis

Resulting pair (consisting of 4 chromatids) is called a tetrad

Question 4

Crossing over

Answer 4

Sometimes chromatids from different chromosomes may twist around each other and segments may trade places

Results in greater genetic variation

Question 5

Metaphase 1

Answer 5

Tetrads line up at the middle

Question 6

Anaphase 1

Answer 6

Homologous chromosomes of each tetrad seperate and move to opposite ends of the cell

Seperate on of tetrad is called disjunction

Accidents during meiosis can alter chromosome number

Abnormal chromosome count is a result of non disjunction

Question 7

Nondisjunction

Answer 7

The failure of homologous pairs to seperate during anaphase 1

The failure of sister chromatids to seperate during anaphase 2

Question 8

Telophase 1

Answer 8

Cytoplasm divides, forming 2 daughter cells which have half of the number of chromosomes as the parent cells

Daughter cells have half the number of chromosomes (haploid)

Question 9

Meiosis 2

Answer 9

Essentially the same as mitosis

The sister chromatids of each chromosome seperate

Results in a total of 4 haploid cells

Question 10

Gametogenesis

Answer 10

Formation of gametes (eggs & sperm)

Occurs in gonads (ovaries & testes)

Must be formed by meiosis

Haploid cells with 23 chromosomes

Question 11

Oogenesis

Answer 11

Formation of eggs / ova

Occurs in ovaries

Primary sex cells (2n) divide by meiosis to form 4 haploid cells which develop into 1 egg & 3 polar bodies

Question 12

Spermatogenesis

Answer 12

Formation of sperm

Occurs in testes

Primary sex cells (2n) divide by meiosis to form 4 haploid cells which develop into 4 sperm cells

Question 13

Fertilization

Answer 13

Fusion of gametes to form a zygote

Question 14

Internal vs. External fertilization

Answer 14

Internal - sperm & egg unite in fallopian tube , occurs in terrestrial animals , few eggs released, few zygotes form , zygotes are developed in the females body

External - sperm & egg unite outside the females body , occurs in aquatic animals , many eggs released , many zygotes form , zygotes are not developed within the females body

Question 15

Karyotype

Answer 15

Ordered arrangement of a cells chromosomes

Pairs 1-22 are called autosomes

23rd pair is a sex chromosome (xx / xy)

Question 16

Hermaphroditism

Answer 16

Hermaphrodite is an organism that contains both male and female gonads, and is able to produce both sperm and eggs

Question 17

Parthenogenesis

Answer 17

Development of an unfertilized egg into an adult animal