voice of the genome Flashcards
how is DNA organised in a bacterial cell?
- large circular DNA
*DNA not associated with histone proteins - several small plasmids
- located in the cytoplasm
what are the roles of the Golgi apparatus and vesicles in the formation and transport of extracellular enzymes?
- vesicles fuse w Golgi apparatus
- modification of proteins inside Golgi apparatus
- protein packaged into secretory vesicles
- vesicles fuse w cell surface membrane
what happens to lysosomes once their contents have been digested?
- lysosome fuses w cell surface membrane
- contents of lysosome released from cell/ exocytosis
how can eukaryotic organisms be differentiated from prokaryotic?
- membrane bound organelles
- mitochondria, RER, SER, nucleus, Golgi, vesicles
- larger ribosomes
- linear DNA associated w histone proteins
- no plasmids in cytoplasm
how can prokaryotic cells be identifies?
- circular DNA/ plasmids
- 70s ribosomes
- pili/ flagellum
- capsule/ mesosome
why can the nucleus not be observed at the end of prophase?
- nuclear membrane is broken down
- DNA is coiled and condensed into individual chromosomes
what are the functions of the Golgi apparatus?
- modifies proteins
- forms vesicles
- removes some water from the protein
where does protein synthesis occur in eukaryotic cells?
80s ribosomes on the endoplasmic reticulum
where is the capsule located in some bacteria?
outside the cell wall
what is the function of plasmodesma?
- cytoplasmic connection between cells
- which allows transport/ communication between cells
why is HCl added to the root tip when observing cell division?
- breaks down middle lamella
- allowing cells to be separated
- to allow light to pass through
why is a stain added to the root tip when observing mitosis?
- makes the chromosomes visible
- so that the stages of mitosis can be identified
how does the shortening of spindle fibres affect mitosis?
- sister chromatids cannot be separated
- anaphase cannot occur
- daughter cells produced with incorrect numbers of chromosomes
what are the events of fertilisation that occur after the acrosome reaction?
- fusion of sperm cell w egg cell membrane
- cortical granules release contents into zone pellucida
- contents of cortical granules react w zoned pellucida
- zona pellucida hardens
- fusion of sperm and egg nuclei
why may offspring be genetically different?
- each zygote is formed from different gametes
- each gamete contains different combinations of alleles
- due to independent assortment/ crossing over
what is meant by the term sex- linked disorder?
- caused by a mutated gene
- located on the X/Y chromosome
- more likely in one gender
how are vesicles involved in the successful fertilisation of an egg?
- cortical granules fuse w egg cell membrane
- releasing enzyme that hardens zone pellucida
how can meiosis lead to genetic variation?
- independant assortment of chromosomes
- crossing over between chromatids
why do some genes show linkage and others show sex linkage?
- there are more genes than there are chromosomes
- linkage relates to genes located on the same chromosome
- sex linkage relates to genes on the same X/Y chromosome
what is the meaning of polygenic?
- a characteristic showing continuous variation
- caused by multiple genes at different loci
how can epigenetic changes affect the development of tissues in the embryo?
- DNA is wrapped around histones
- acetylation of the histone affects binding of RNA polymerase
- methylation of DNA affects transcription of genes
- so gene expression is altered
what is the difference between a tissue and an organ?
a tissue is made if one type of cell and an organ is made of different tissues
what are the decisions that society has to make about the use of embryonic stem cells?
- totipotent so can be used in a wider range of therapies
- source has to be considered
- ethical issues as the use destroys embryos
- research establishments need to be regulated
what is the meaning of the term totipotent cell?
a cell that has the ability to differentiate into all cell types
how do cells become specialised?
- chemical signals cause some genes to be activated
- only activated genes are transcribed
- leads to synthesis of specific proteins which cause cell modification
why can stem cells from the heart not be used to grow cells to repair the cornea?
- not totipotent
- some genes already activated and deactivated
- so cannot specialise into cornea cells
why does age affect the time taken to recover from injuries?
- time will increase
- due to fewer stem cells with age
- to replace cells in tissues
what is meant by the term stem cell?
- undifferentiated cell
- that can give rise to specialised cells
- that can divide to produce more stem cells
compare and contrast the results of meiosis and mitosis in the production of gametes from stem cells
- both increase the number of cells
- mitosis produces diploid, meiosis produces produces haploid
- meiosis produces genetically different, mitosis produces genetically identical
- mitosis results in 2 daughter cells, meiosis 4
why may an individual have a greater adult height than their biological parents?
- height is affected by environment as well as genotype
- eg higher protein diet
- polygenic inheritance
- offspring can inherit a mixture of alleles from both parents
what is the effect of Ca+ on the acrosome?
- in presence, acrosome fuses w cell membrane
- causes acrosome reaction to take place
What is meant by the term allele?
Alternative form of a gene
Found at the same locus
Explain what is meant by an inherited recessive disorder
Caused by a faulty allele
That is only expressed if genotype is homo recessive
explain why sperm cells with 2 flagella may reduce fertility
affect motility
may prevent sperm from reaching egg
preventing fertilisation
describe how the acrosome is involved in the digestion of the zone pellucida
membrane of the acrosome fuses with the plasma membrane of the sperm cell
releasing enzymes
by exocytosis
what is the role of the acrosome?
to release enzymes to digest the zone pellucida
what are the function of amyloplasts?
store starch granules
how does independent assortment over produce gametes w new combos of alleles?
diff combos of chromosomes
how may crossing over differ in sex chromosomes?
crossovers cannot form between some sections of X and Y chromosome
not homologous
Y is shorter
alleles on X that aren’t on Y
describe how a slide can be prepared from a root tip sample
stained w toluidine blue
use of HCl to prepare tissue sample
tissue heated
tissue squashed under coverslip
what stage of interphase has the greatest increase in cell size
G1
describe what happens inside a cell during prophase of mitosis
nucleolus breaks down
centrioles move to opposite poles of the cell
to form spindle fibres
nuclear membrane breaks down
chromosomes condense
explain why DNA is replicated before mitosis begins
ensure that one copy of each chromosome in each daughter cell
ensure daughter cells are genetically identical
explain how large numbers of cells with the same phenotype can be produces in a tissue
phenotype determined by genotype and effect of environment
mitosis produces cells w same genotype
name the part of a chromosome that is occupied by a gene
locus
describe how each gamete receives only one allele of each gene
homologous chromosomes are separated
sister chromatids separated
spindle fibres pull chromosomes to opposite poles of the cell
give the reason for the high density of mitochondria found in the mid piece of a sperm cell
energy/ATP for movement of flagellum
explain why genes found on the sex chromosome pair have a pattern of inheritance that is different from genes found on other chromosome pairs
X chromosome carries genes not present on the Y chromosome
males have only one copy of some genes
it will be expressed
state how a graph provides evidence that a characteristic shows polygenic inheritance
shows continuous variation
what does polygenic inheritance mean
controlled by more than one gene
describe how a tissue differs in structure from a system
tissue contains only type of cell
system contains many diff tissues/ organs
describe how stem cells can give rise to different types of cell
different stimuli activate different genes
genes activated are transcribed/ mRNA produced from active genes
mRNA translated to produce proteins
proteins determine structure/ function of cells
diff genes activated/ proteins produced result in diff types of cell being produced
explain what is meant by the phrase: the null hypothesis was rejected at the 5% significance level for this investigation
there is a correlation
as there is only a 5% likelihood of these results being produced by chance
