Exam question Flashcards
Explain the role of the cell cycle (2)
- growth of an organism
- repair of tissues
- asexual production
Suggest how the cell cycle will be affected in cells that have become cancerous (2)
- shorter growth/G phase/interphase
- shorter/faster cycle
- controls/stops not working effectively (uncontrollable cell division)
- cells do not become specialised
Describe the process by which cells usually become specialised following cell division (3)
- chemical stimulus
- some genes active some genes inactive
- only active genes are transcribed
- mRNA made from active genes
- mRNA is transcribed into specific proteins
- protein determines cell structure and function
Explain how DNA methylation can modify the activation of a gene (3)
- methyl groups attach to DNA bases
- prevents transcription of gene
- transcription factors/RNA polymerase cannot bind to the promotor region of gene/DNA
- deactivating/switching off the gene
Give the meaning of the term polygenic (2)
- a characteristic showing continuous variation
- caused by multiple genes at different loci
Explain how groups of cells can produce the same enzyme (3)
- genes can be activated or deactivated
- genes receive the same stimulus
- gene switched on for the enzyme
- results in the production of mRNA for the enzyme
Describe how the cells process a polypeptide and secrete it as an enzyme (4)
- polypeptide is folded in the rough endoplasmic reticulum (tertiary structure)
- rER packages polypeptide into transport vesicle
- transport vesicle fuses with Golgi apparatus
- polypeptide is modified inside the Golgi apparatus
- Golgi packages enzyme into secretory vesicle which fuses to the cell surface membrane
- enzyme released by exocytosis
Explain the advantages of using the patients own stem cells from instead of using stem cells from a donor (2)
- no risk of rejection
- genetically identical cells
- less risk of infection
Compare and contrast the structure and function of lysosomes and acrosomes (3)
similarities:
- both contain digestive enzymes
- both have single membrane/membrane bound organelles
differences:
- lysosome is spherical whereas an acrosome is curved
- lysosome involved in intracellular digestion whereas acrosome is involved in extracellular digestion
- lysosome is involved in the breakdown of cell components/virus whereas acrosome is involved in digesting the outer layer of an egg cell/zona pellucida
Explain how cortical granules ensure that the egg cell is diploid after fertilisation (4)
- cortical granules are released from the egg
- cortical granules fuse with the zona pellucida
- cortical granules release {chemicals/enzymes} which causes the hardening of the zona pellucida
- preventing more than one sperm entering the egg cell
- egg cell and sperm cell are haploid and fuse together during fertilisation
what is meant by the term organ system (1)
a group of organ working together to carry out one or more specific function
State what is meant by the term tissue (1)
a group of similar cells working together for a specific function
Explain how an egg cell is specialised for its function (2)
- haploid egg cell so when it is fertilised it becomes diploid
- contains lipid droplets as a source of energy
- contains cortical granules to prevent polyspermy/harden the zona pellucida
Gametes contain mitochondria. Describe the function of mitochondria in sperm cells (2)
- they carry out aerobic respiration
- provide ATP/energy
- to move the flagellum
Explain the importance of meiosis in the production of gametes (4)
- halves the chromosome number
- to produce a haploid nucleus
- so that the diploid number of chromosomes is restored at fertilisation
- allows genetic variation
- through crossing over
- and independent assortment
Explain why colour blindness is more common in males than in females (2)
- colour blindness occurs on the recessive allele of the X chromosome
- males only need one recessive allele whereas women need to inherit two
Explain what is meant by the term sex-linked disorder (2)
- caused by a faulty gene
- located on the X or Y chromosome
- disorder is more likely to be inherited in one gender than the other
Describe how crossing over gives rise to different combinations of alleles in gametes (2)
- exchange of alleles
- between two sister chromatids
Explain how independent assortment gives rise to genetically varied gametes (2)
- random arrangement of chromosomes
- maternal and paternal chromosomes (chromosomes from homologous pairs)
Explain how independent assortment gives rise to genetically varied gametes (3)
- crossing over/independent assortment
- independent assortment results in different combination of alleles
- crossing over results in different allele combinations
What is meant by the term allele (1)
alternate from of a gene
Explain the role of the spindle in mitosis (2)
- to attachment/binding to the centromeres
- to separate sister chromatids/chromosomes
Devise an investigation to study the relationship between the distance from the tip of a root and the percentage of cells undergoing nuclear division (5)
- samples from different distances from root tip
- use an eyepiece graticule to measure distance from tip
- details of procedure (hydrochloric acid, maceration)
- toluidine blue stain used
- calculate mitotic index
number of cells undergoing mitosis/total number of cells in field view
Describe what happens in the cell during the telophase stage of mitosis (4)
- chromosomes decondense
- spindle fibres break down
- nuclear envelope reforms
- two nuclei are present
- nucleoli reform
