3.2 - From one to many: the cell cycle Flashcards
What are autosomes?
all the chromosomes which aren’t sex chromosomes
What is the locus?
position of a gene on a chromosome
What are the 2 situations when are genes inherited independently?
- if they are found on different chromosomes
- if they are far apart on same chromosome
What do we say when 2 genes have a locus on the same chromosome?
linkage
what is likely to happen when 2 genes are linked?
they will be passed on as a pair of genes/inherited together into the same gamete
What is autosomal linkage?
different genes with the same locus on the same autosome will tend to be passed on as a pair to the same gametes
How does genetic variation occur through autosomal linkage?
independent assortment
What are the 4 stages of mitosis?
- prophase
- metaphase
- anaphase
- telophase
What happens in prophase?
- chromosomes condense & become visible as 2 strands called chromatids
- 2 poles of the spindle are formed
- nuclear envelope is broken down
What happens during interphase (before mitosis)?
- synthesis of new cell organelles
- DNA replication
What happens during metaphase?
- chromsomes’ centromeres attach to spindle fibres at equator
What happens during anaphase?
- centromeres split
- spindle fibres shorten
- pulls one chromatid of each chromosome to each of the poles
- spindle breaks down
What happens in telophase?
- chromosomes unravel & nuclear envelope reforms, so 2 sets of genetic information become enclosed in separate nuclei
What is widest part of the spindle called?
equator
What is the more unofficial stage of mitosis?
cytoplasmic division
What happens during cytoplasmic division?
- 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
What are the sex chromosomes for females? And for males?
XX - females
XY - males
What is sex linkage?
when genes on the sex chromosomes are found at the same locus and passed on with those that determine sex
What is a stem cell? (2 points)
- undifferentiated cell
- that can divide to produce more stem cells
What is a multipotent stem cell?
a cell that can give rise to a few types of specialised cells
What is a pluripotent stem cell?
a cell that can give rise to many types of specialised cells, but not placental cells
What is a totipotent stem cell?
a cell that has the ability to divide into all cell types
How do cells become specialised?
- 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
define transcription factor.
protein that controls the activation of genes
