2.6 New cells from old Flashcards
What is always constantly happening to multicellualr organisms
Contrinually replacing new cells, eahc of the new cells must recieve a copy of genetic info stored in DNA
When does DNA replication occur
Interphase - prior to cell division
What sorts of chromosomes do somatic cells contain
Pairs - maternal and paternal.
What are pairs of maternal and paternal chromosomes called
Homolgous pairs
What is a cell consisiting of homologous pairs called
Diploid (2n)
In humans, one chromosome from each homologous pair is inherited from either parent. t or f
True
What sort of chromosomes do germ cells contain
Only one chromosome from each homologous pair
What are cells that do not contain a homologus pair called
Haploid
Two germ cells fuse to form a haploid cell true or false
False. These cells are already haploid and fuse to form a diploid zygote
How do prokaryotes reproduce
Binary fission
Comapre the DNA in parent and daughter cells from binary fission
Daughter cells contain same number and type of chromosomes as parent, preserving the genetic information from one parent to the next
Describe the process of binary fission
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
Describe asexual reproduction
Formation of offspiring from a single parent without fertilistion. Examples include binary fission, vegetative reproduction and budding of yeast cells.
What is the only source of genetic variation in asexual reproduction
mutation - a spontaneous or induced change in the genetic material
Why would cells need to be replaced
If damaged or worn out-e.g. skin cells, for growth
Name the sequences in the cell cycle
Interphase (DNA replication)
Mitosis (divison of the cytoplasm)
Cytokenisis (division of the cell)
What happens in interphase
Enlargement of cell due to synthesis of new cell components including new organelles and replicated DNA and intake of water
What occurs in prophase
-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)
What are centrioles made up of
microtubules - plant cells don’t have centrioles
What occurs in metaphase
chromsomes line up at the equator 9metaphase plate) and attache to the spindle by centromeres. Siste chromatids face opposite poles
What occurs during anaphase
sister chromatids seperate and move to opposite poles (spindle contraction separates and centromeres and pulls the chromatids towards the poles
Describe what occurs during telophase
new nuclear envelopes form around both sets of chromosomes
nucleoli reappear
Chromsomes uncoil, reverting back to chromatid
what occurs during cytokensis
the cytoplasm and it’s contents are divded between two new daughter cells.
describe some similarities between the result of binary fisiions and mitosis
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
