2.6 New cells from old

Question 1

What is always constantly happening to multicellualr organisms

Answer 1

Contrinually replacing new cells, eahc of the new cells must recieve a copy of genetic info stored in DNA

Question 2

When does DNA replication occur

Answer 2

Interphase - prior to cell division

Question 3

What sorts of chromosomes do somatic cells contain

Answer 3

Pairs - maternal and paternal.

Question 4

What are pairs of maternal and paternal chromosomes called

Answer 4

Homolgous pairs

Question 5

What is a cell consisiting of homologous pairs called

Answer 5

Diploid (2n)

Question 6

In humans, one chromosome from each homologous pair is inherited from either parent. t or f

Answer 6

True

Question 7

What sort of chromosomes do germ cells contain

Answer 7

Only one chromosome from each homologous pair

Question 8

What are cells that do not contain a homologus pair called

Answer 8

Haploid

Question 9

Two germ cells fuse to form a haploid cell true or false

Answer 9

False. These cells are already haploid and fuse to form a diploid zygote

Question 10

How do prokaryotes reproduce

Answer 10

Binary fission

Question 11

Comapre the DNA in parent and daughter cells from binary fission

Answer 11

Daughter cells contain same number and type of chromosomes as parent, preserving the genetic information from one parent to the next

Question 12

Describe the process of binary fission

Answer 12

DNA untwists, allowing enzymes to aid it’s replication.

Each set of DNA is attached by proteins to the cell membrane. as the cell grows/elongates it pulls chromosomes apart

A new cell wall is then created across the equator, forming two daughter cells. Each daughter celll is identical to each other and to the original paretn cell

Question 13

Describe asexual reproduction

Answer 13

Formation of offspiring from a single parent without fertilistion. Examples include binary fission, vegetative reproduction and budding of yeast cells.

Question 14

What is the only source of genetic variation in asexual reproduction

Answer 14

mutation - a spontaneous or induced change in the genetic material

Question 15

Why would cells need to be replaced

Answer 15

If damaged or worn out-e.g. skin cells, for growth

Question 16

Name the sequences in the cell cycle

Answer 16

Interphase (DNA replication)
Mitosis (divison of the cytoplasm)
Cytokenisis (division of the cell)

Question 17

What happens in interphase

Answer 17

Enlargement of cell due to synthesis of new cell components including new organelles and replicated DNA and intake of water

Question 18

What occurs in prophase

Answer 18

-Chromatin condenses forming chromosomes (each has two identical chromatids joined at a region called the centromere)

Nuclear envelop and nucleoli disappear

Centrioles divide to form 2 pairs which move to opposite poles

Spindle apparatus forms (centrioles + spindle fibres)

Question 19

What are centrioles made up of

Answer 19

microtubules - plant cells don’t have centrioles

Question 20

What occurs in metaphase

Answer 20

chromsomes line up at the equator 9metaphase plate) and attache to the spindle by centromeres. Siste chromatids face opposite poles

Question 21

What occurs during anaphase

Answer 21

sister chromatids seperate and move to opposite poles (spindle contraction separates and centromeres and pulls the chromatids towards the poles

Question 22

Describe what occurs during telophase

Answer 22

new nuclear envelopes form around both sets of chromosomes
nucleoli reappear

Chromsomes uncoil, reverting back to chromatid

Question 23

what occurs during cytokensis

Answer 23

the cytoplasm and it’s contents are divded between two new daughter cells.

Question 24

describe some similarities between the result of binary fisiions and mitosis

Answer 24

genetic material is replicated and each daughter cell recieves an identical copy. cells formed due to binary fission and mitosis are genetically identical to eahc other and their parent. therfore number and type of chromsomes are identical to parent