Bio Lecture 8

Front 1

reproduction

Back 1

one of characteristics of living things.
production of new organisms or cells from pre-existing ones
-occurs through cell division

Front 2

chromosomes (4)

Back 2

a. consist of DNA and histone proteins
b. found in the cell nucleus
c. small segments of DNA=genes

Front 3

chromosomes (cont'd)

Back 3

must undergo duplication
a. two sister chromatids
b. held together by a centromere

Front 4

2 modes of reproduction

Back 4

1. asexual reproduction--mitosis
2. sexual reproduction--meiosis

Front 5

mitosis-interphase

Back 5

1. cell spends most of its life here
2. chromosomes as chromatin
3. chromosomes duplicated near end of interphase

Front 6

mitosis-prophase

Back 6

1. chromatin condenses--chromosomes become visible
2. centrosomes begin moving to poles
3. spindle fibers begin to appear
4. nuclear envelope begins to disappear

Front 7

mitosis-metaphase

Back 7

1. chromosomes align along equator
2. spindle fibers attach to chromosomes

Front 8

mitosis-anaphase

Back 8

1. centromeres divide -- chromatids become daughter chromosomes
2. daughter chromosomes begin moving to opposite poles

Front 9

mitosis-telophase and cytokinesis

Back 9

1. nuclear envelopes start to re-appear
2. chromosomes go back to chromatin
3. cytokinesis occurs--the cleavage furrow

Front 10

major functions of mitosis

Back 10

1. growth and repair in multicellular organisms
2. asexual reproduction
a. binary fission -- eg amoebas
b. budding -- eg yeasts
c. vegetative reproduction in plants -- stolons and rhizomes

Front 11

sexual reproduction

Back 11

1. cells have a diploid (2N) number
2. diploid number for humans (46)
3. chromosomes exist as homologous pairs
4. sex chromosomes--pair that determines sex
5. autosomes- chromosomes not involved in sex determination

Front 12

overview

Back 12

-diploid zygote formed by fusion of gametes (fertilization)
-two diploid parents produce gametes
-gametes are haploid (1N)
-gametes are produced in germ tissue (gonads)
-gametes produced by meiosis

Front 13

overview of meiosis

Back 13

-consists of 2 nuclear divisions (meiosis I, II)
-first division reduces the number of chromosomes to the haploid condition
-second division is mitosis
-end result is 4 haploid cells

Front 14

meiosis I-interphase I

Back 14

1. just like mitosis
2. chromosomes duplicated near end

Front 15

meiosis I-prophase I

Back 15

1. homologous chromosomes form tetrads
2. crossing-over occurs--homologous chromosomes exchange part

Front 16

meiosis I- metaphase I

Back 16

1. tetrads align along cell equator
2. spindle fibers attached to centromeres

Front 17

meiosis I-anaphase I

Back 17

1. disjunction--tetrads separate and move towards opposite poles
2. here's where chromosome number is reduced to the haploid number

Front 18

meiosis I- telophase I

Back 18

1. cytokinesis
2. 2 haploid daughter cells

Front 19

meiosis II

Back 19

1. basically mitosis
2. results in 4 haploid daughter cells

Front 20

meiosis in humans (males)

Back 20

germ cells in gonads are capable of meiosis
-spermatogenesis in males
1. occurs in testis cells--spermatocytes
2. 4 haploid daughter cells produced
3. daughter cells develop intom otile gametes called spermatozoa

Front 21

meiosis in humans (females)

Back 21

called oogenesis
1. occurs in cells in the ovary -- oocytes
2. 4 haploid daughter cells produced
3. 1 daughter cell develops into a gamete called ovum (egg)
4. 3 daughter cells become small, non functional polar bodies

Front 22

importance of meiosis

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-haploid gametes keep diploid number the same from one generation to next
-crossing over is a source of genetic variation

Front 23

bad meiosis

Back 23

sometimes mistakes occur during
-these errors can result in gametes and zygotes with wrong number of chromosomes