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
State what is meant by the term polygenic inheritance (2)
- many genes at different loci
- that code for the same characteristic
Explain why an individual may have a greater adult height than their biological parents (4)
- height is affected by the environment as well as genotype
- height is an example of polygenic inheritance
- therefore offspring can inherit a mixture of alleles from both parents (increasing height)
- environmental factor, diet
Describe the roles of the organelles that are involved in the synthesis and secretion of digestive enzymes (4)
- polypeptide is synthesised on the ribosomes on the rough endoplasmic reticulum
- polypeptide enters rER and is folded into the tertiary structure
- rER packages protein/enzyme into transport vesicle that moves and fuses to the Golgi apparatus
- protein/enzyme is modified inside of the Golgi apparatus
- modified protein/enzyme is packaged into a secretory vesicle by Golgi apparatus
- secretory vesicle moves and fuses to the cell surface membrane and the enzyme is released by exocytosis
Describe how you could use a plant tissue culture technique to show totipotency in plant seedling
- use an explant
- use agar
- agar contains growth hormones/substances
- use of aseptic technique
- covering the top of the container to prevent contamination/water loss
- place under light bank
- growth time of 1-6 weeks
- look for roots/leaves forming
Describe the difference between a totipotent stem cell and a pluripotent stem cell (2)
- totipotent stem cells can give rise to any cell
- pluripotent stem cells cannot give rise to all cells in the body (give rise to most cells)
Describe the decisions that society has to make about the use of these embryonic stem cells (3)
- embryonic stem cells are totipotent and can be used in a wider range of therapies
- source of embryonic stem cells has to be considered
- moral/ethical issues since using embryonic stem cells kills the embryos
- the need for research establishments to be licensed
