3.2 - From one to many: the cell cycle

Question 1

What are autosomes?

Answer 1

all the chromosomes which aren’t sex chromosomes

Question 2

What is the locus?

Answer 2

position of a gene on a chromosome

Question 3

What are the 2 situations when are genes inherited independently?

Answer 3

1. if they are found on different chromosomes
2. if they are far apart on same chromosome

Question 4

What do we say when 2 genes have a locus on the same chromosome?

Answer 4

linkage

Question 5

what is likely to happen when 2 genes are linked?

Answer 5

they will be passed on as a pair of genes/inherited together into the same gamete

Question 6

What is autosomal linkage?

Answer 6

different genes with the same locus on the same autosome will tend to be passed on as a pair to the same gametes

Question 7

How does genetic variation occur through autosomal linkage?

Answer 7

independent assortment

Question 8

What are the 4 stages of mitosis?

Answer 8

1. prophase
2. metaphase
3. anaphase
4. telophase

Question 9

What happens in prophase?

Answer 9

• chromosomes condense & become visible as 2 strands called chromatids
• 2 poles of the spindle are formed
• nuclear envelope is broken down

Question 10

What happens during interphase (before mitosis)?

Answer 10

• synthesis of new cell organelles
• DNA replication

Question 11

What happens during metaphase?

Answer 11

• chromsomes’ centromeres attach to spindle fibres at equator

Question 12

What happens during anaphase?

Answer 12

• centromeres split
• spindle fibres shorten
• pulls one chromatid of each chromosome to each of the poles
• spindle breaks down

Question 13

What happens in telophase?

Answer 13

• chromosomes unravel & nuclear envelope reforms, so 2 sets of genetic information become enclosed in separate nuclei

Question 14

What is widest part of the spindle called?

Answer 14

equator

Question 15

What is the more unofficial stage of mitosis?

Answer 15

cytoplasmic division

Question 16

What happens during cytoplasmic division?

Answer 16

• the whole cell divids and one nucleus moves into each cell to create two genetically identical daughter cells
  (in animal cells) - involves constriction of cytoplasm & (in plant cells) - a new cell wall is formed

Question 17

What are the sex chromosomes for females? And for males?

Answer 17

XX - females
XY - males

Question 18

What is sex linkage?

Answer 18

when genes on the sex chromosomes are found at the same locus and passed on with those that determine sex

Question 19

What is a stem cell? (2 points)

Answer 19

• undifferentiated cell
• that can divide to produce more stem cells

Question 20

What is a multipotent stem cell?

Answer 20

a cell that can give rise to a few types of specialised cells

Question 21

What is a pluripotent stem cell?

Answer 21

a cell that can give rise to many types of specialised cells, but not placental cells

Question 22

What is a totipotent stem cell?

Answer 22

a cell that has the ability to divide into all cell types

Question 23

How do cells become specialised?

Answer 23

• a stimulus acts on unspecialised cells (stem cells)
• activator & repressor molecules bind to promoter regions on the DNA sequence
• some genes are switched on & others are switched off
• active genes are transcribed to produced mRNA
• mRNA is then translated to synthesise specific proteins
• proteins have the ability to modify the cell

Question 24

define transcription factor.

Answer 24

protein that controls the activation of genes