End of Year Exam Year 11 Flashcards
Stages of Mitosis
Prophase
Metaphase
Anaphase
Telophase
Differences between Mitosis in a plant and animal cell
The most important and observable difference in the plant and animal cells mitosis is the cytokinesis.
In plant cells, a new cell plate is formed between the daughter cells for the future cell wall, while in animal cells the cell membrane constricts to separates the parent cell into daughter cells.
Prophase
Chromatin threads condense and become visible as pairs of chromatids, held together by a centromere
Centrioles move to opposite ends of the cell and microtubules begin to radiate from them
Some microtubules join to form a framework of fibres called a spindle
Nucleolus disappears from view and the nuclear membrane breaks down
Metaphase
Chromatid pairs move to the centre of the cell and line up along the metaphase plate
The centromere of each pair is attached to a spindle fibre
Anaphase
Spindle fibres attached to the chromatids help to pull them apart.
Chromatids separate at the centromere and move to opposite poles of the spindle and the spindle fibres contract
Now each former chromatid is called a chromosome
Telophase
Two sets of chromosome form tight clusters at each pole of the cell
Chromosomes de-condense as the chromatin unwinds and becomes less visible
New nuclear envelop forms, nuclei reform and the spindle disassembles
Cytokinesis
The division of a cell following mitosis and meiosis, when the cytoplasm divides and the cell splits into 2 daughter cells
When does cytokinesis occur
Cytokinesis begins in anaphase in animal cells and prophase in plant cells, and terminates in telophase in both, to form the two daughter cells produced by mitosis
G1 Phase
The cell produces new proteins, grows and carries out normal tasks for the body; it ends when the DNA begins to replicate
S Phase
duplicates of DNA molecules are formed
G2 Phase
preparation for cell division
M Phase
the cell divides into 2 daughter cells
G0 Phase
indicates the non-proliferating state (extended G1 phase but not preparing to replicate DNA and divide)
Type of bond in nucleotides, forming DNA
Hydrogen bonds
between the bases that are across from one another hold the two strands of the double helix together
Components of DNA and Primes
Phosphate
Sugar
Nitrogenous Bases
ALWAYS 5’ to 3’
5 prime, 3 prime rule in DNA synthesis
DNA polymerase only synthesizes DNA in the 5’ to 3’ direction only. The difference between the leading and lagging strands is that the leading strand is formed towards replication fork, while the lagging strand is formed away from the replication fork.
All types of asexual reproduction in plants and animals.
binary fission, fragmentation, budding, vegetative reproduction, spore formation and agamogenesis
Cells divide for the purpose of
- Repair
- Reproduction
- Growth
- replacement of damaged or dead cells
Mitosis
This is a process whereby DNA is replicated and a new cell is produced
Mitosis is used to…
Produce new body cells and is therefore responsible for the growth of the organism and repair/ replacement of cells
Growing regions of organisms contain many cells undergoing mitosis. Eg plant shoot and root tips
asexual reproduction advantages
- Can reproduce without a mate so does not expend time and energy to search for a mate
- Can reproduce a large number of offspring rapidly
- Stable moments with very little change are favourable for organisms to reproduce asexually
asexual reproduction disadvantages
- Offspring produced are genetically identical to each other and to the parent. This causes no or very little genetic variation within a population
- Any mutation in the parent cell can cause harmful effects on the survival ability of the offspring
- Environmental change could be deadly to all individuals
sexual reproduction
In sexual reproduction, two parent contribute genetic information to produce unique off spring
- Normal body cells ( all cells excerpt sex cells) are called somatic cells
- this genetic information is contained in our sex cells which are called gametes ( sperm and egg) sex cells are formed by meiosis
Meiosis 1: Interphase 1
Chromosomes are not visible. DNA is replicated
Meiosis: Prophase 1
Chromosomes appear, becoming thicker and shorter, they are double stranded
Homologous chromosomes align and pair closely or synapse
Crossing over occurs allowing for the exchange of genetic material to produce new combinations of genetic instructions ( one genetic variation )
Meiosis: Metaphase 1
Homologous chromosomes form two lines along the equator of the cell. Different arrangements are possible ( independent assortment) which increases genetic variation of offspring
Meiosis: Anaphase 1
The Homologous chromosomes separate when their chromosomes are pulled to opposite ends of the cell
Meiosis: Telophase 1 and Cytokinesis
- Chromosomes become thinner
- new nuclear membranes form around each group of double - stranded chromosomes
- cytokinesis occurs producing two new cells
Meiosis: Prophase 2
The double stranded chromosomes condense
Meiosis: Metaphase 2
Chromosomes line up in a single line along the equator
Meiosis: Anaphase 2
The chromosomes are pulled apart and move towards the poles
Meiosis: Telophase 2 and Cytokinesis
- New nuclear membrane forms around each group of chromosomes
- cytokinesis produces two new cells
Non-disjunction of chromosomes
If two chromosomes fail to seperate at anaphase then either two copies of a chromosome are present when there should be one or a copy of a chromosome may be missing
No two offspring are the same
How is this achieved:
- Crossing over and recombination
2. Independent assortment
Blastocyst
The blastocyst consists of three layers:
An inner cell mass, which will form the tissues of the embryo, a fluid filled cavity and an outer layer which will become part of the placenta
Stem cells
Stem cells are undifferentiated cells which have the ability to differentiate into organ or tissue specific cells with specialised functions. Eg ( nerve cells, blood cells, heart cells)
Stem cells can be either embryonic ( from the blastocyst ) or adult
Types of stem cells - totipotent
A cell that can differentiate into all different cell types ( the total organisms) (embryonic)
Types of stem cells - pluripotent
A cell that can differentiate into many different cell types ( embryonic )
Types of stem cells - multipotent stem cells
A cell that can differentiate into a number of closely related cell types. Eg a multipotent blood cell can develop into a red or white blood cell ( adult )
Types of stem cells - unipotent stem cells
A cell that can only produce cells of their own type ( adult)
Homologous chromosomes
Pair of chromosomes that are the same size, same appearance and same genes.
Describe some ethical concerns regarding the use of cloning technology
Could be sued for experimental purposes that could result in some sort of animal / human hybrid to be created. Would be an ethical dilemma at the doing where the creature was experimented on or euthanised at the experiment. Is it human enough to be considered murder ?
Binary Fission
After replicating its genetic material, the cell divides into two nearly equal sized daughter cells. Most common form of reproduction in prokaryotes (bacteria)
Spore Formation
Occurs in fungi, plants algae and bacteria
- One cell enlarges and forms a sporangium ( spore sac)
- Nucleus and cytoplasm of this cell divides many times to form daughter cells called spores. ( of these spores have just one copy of each chromosome)
- The spores are covered with a thick wall called the cyst
- When mature, the sporangium bursts and releases spores
- The spores then germinate when favourable conditions are present
Budding (hydra)
New individuals form from outgrowths (buds) on mature organisms. These outgrowths grow by mitotic cell division
Budding is common in plants and fungi. It also occurs in certain animals particularly the hydra (sponges)
Vegetative propagation
- like budding for plants
- A method of reproducing plants without pollination
- vegetative parts of plants such as stems, leaves and roots are separated from the plant and allowed to take root and grow
- this is commonly practiced by horticulturists to obtain large quantities of valuable plants
Explain how crossing over and independent assortment contribute to genetic diversity in offspring
Crossing over results in the exchange of genetic material between sister chromosomes. Resulting in a chromosome that contains mostly the genes from one parent plus some swapped from the chromosome of the other parent
Eg. So if we have an organism that has five pairs of chromosomes in it, five from the mother and five from the father. During anaphase one, it is possible that all the chromosomes from the mother go together into one cell and the other five chromosomes from the father into the other cell.
It is also possible that three chromosomes from the mother ( eg. Chromosomes number 1,2&3 )plus 2 chromosomes from the father ( eg chromosomes 4&5 ) went into on cell and the remaining chromosomes ended up into thin other cell ( eg 4&5 from mother and 1,2&3 from father )
Genome
A genome is an organisms complete set of genetic instructions ( DNA)
An organisms genome can be determined by looking at an organisms haploid set of chromosomes with all the genes they contain
Each genome contains all of the information needed to build that organism and allow it to grow and develop
Genomes size varies greatly between organisms
Genes and inheritance
- Genes are sections of DNA in chromosomes that contains the information for the production of proteins
- Proteins are responsible for the expression of genes as characteristics for traits: such as eye colour
- Since genes are inherited, traits are also inherited
Alleles
alternative forms of a gene.
In sexually reproducing organisms, most cells have a homologous pair of chromosomes / one from each parent ).
Chromosomes from a homologous pair have genes that control the same trait at the same position ( locus )
These pair of genes are said to be alleles
Heterozygous/Homozygous
Alternative forms of a given gene are called alleles and they can be dominant or recessive.
When an individual has two of the same allele, weather dominant or recessive, they are homozygous.
Heterozygous means having one each of two different alleles.
DNA
DNA stands for deoxyribosenucleic acid
The building blocks of DNA are called nucleotides
Nucleotides comprise of 3 components
- A sugar ( deoxyribose )
- A phosphate group
- Nitrogenous base ( adenine, thymine, guanine and cytosine )
DNA is built from nucleotides that join to form a chain
the genome as the sum total of
an organism’s DNA measured in the number of base pairs
contained in a haploid set of chromosomes
the role of genomic research since the Human Genome Project,
with reference to the
sequencing of the genes of many organisms, comparing relatedness between species, determining gene function and genomic applications for the early detection and diagnosis human diseases.
The goal of the project was to determine the precise order sequence of bases in DNA which make up the human genome
benefits of HGP
- comparative genomics
- determine gene function
- disease detection
Chromosome structure
Histone: proteins organise the DNA into tightly coiled structures ( visible chromosomes) during cell division
Coiling: into compact structures allows the chromatids to separate without tangling during cell division
Chromosome features:
Chromosomes can be identified by noting : Banding patterns Position of centromeres Presence of satellites Length of chromatids
These features enable homologous pairs to be matched and therefore accurate karyotypes to be made.
Inheritance
The acquisition of characteristics that are genetically passes on from parents to their offspring. Eg eye colour, height , hair colour
Genes
The small part of a chromosome responsible for heredity
Traits
They are the characteristics of an organism that are expressed by genes
They may be physical characteristics or behavioural ones
Eg ability to roll the tongue
Complete dominance (dominant/recessive)
Some phenotype traits can be described as dominant or recessive
A trait is dominant when it appears in the phenotype of a heterozygote
Recessive traits only appear in the phenotype of homozygous, not heterozygous ( B is dominant over b, b is recessive )
Carriers
A carrier is a heterozygous that has the allele for a recessive trait but does not show the trait. Eg Bb
Some parents are both carriers for recessive disorders and may not realise until they have a baby with a disorder.
Eg cystic fibrosis
This is the most common recessive disorder. In Australia 1 in 25 people are carriers of CF. it is screen for at birth
Co-dominance
In some cases one allele will not be completely dominant over the other. When this happens the heterozygote will exhibit both traits
Eg human ABO gene, cattle
Incomplete dominance
In some cases both alleles are equally dominant. When this happens the heterozygote will exhibit a mixture of the traits
Eg red and white flowers = pink
What influences a phenotype?
An organisms phenotype is influenced by both its genotype and environmental factors
Phenotype = genotype + environment
Mutations
These are changes to the DNA sequence. They produce new alleles which may produce new phenotypes.
Environmental factors that can influence the phenotype
Diet, temp, intrauterine environment, soil pH
Eg diet
A disorder where the enzyme that digests some proteins is not produced. If a high protein diet is consumed babies suffer brain damage. If low protein diet is consumed there is no brain damage.
Monogenetic inheritance
Traits controlled by a single gene are called monogenic
Only a few phenotypes are produced. This is known as discontinuous variation.
Eg human blood types
Polygenetic inheritance
Traits controlled by several genes are called polygenic
They do not exhibit a dominant / recessive effect
Each gene has a small and cumulative effect on the phenotype
This is known as continuous variation. Graphing the distribution of the trait will usually produce a bell curve
Eg human skin colour, eye colour and height
Epigenetics
This is the study of how cells with identical gene types can show different phenotypes
It refers to all changes to genes, apart from changes to their base sequences, that bring about phenotypic changes.
Autosome
Any chromosome that isn’t a sex chromosome
Describe the structure of DNA
The three dimensional structure of the DNA: composed 2 sugar- phosphate “backbones “ joined by bases. The structure is like a twisted ladder. The base repeating unit of the DNA molecule is a nucleotide
What are DNA bases and how do they relate to genes
The genetic code is made up of a sequence of bases. Eg ATTTCGAGCT. The bases are adenine, thymine, guanine and cytosine, which pair to form the rungs of the DNA ladder. A particular sequence codes for a given gene
How do genes and the environment interact? Give an example
The genetic code is passed into the next generation, but interacts with environment factors. An example would be height in humans. A person will only reach genetic potential of the genes if given sufficient nutrients to grow fully . In plants growing in adverse conditions ( eg string winds in coastal area) may not be able to grow to their full height but would do so in benign conditions.
Chromosomal abnormalities
Chromosomal abnormalities refer to changes in the chromosome structure. Eg (loss or gain of segments) or a change in the normal number of chromosomes ( eg extra chromosome 21)
Down Syndrome
a condition of intellectual disability and associated physical disorders caused by an extra copy of chromosome 21.
Kleinfelter’s Syndrome
male with more than one X chromosome (XXY)
Turner’s Syndrome
A genetic defect in which affected women have only one X chromosome, causing developmental abnormalities and infertility.
DNA sequencing
DNA sequencing is the process of determining the precise order of nucleotides within a DNA molecule. It includes any method or technology that is used to determine the order of the four bases- adenine, guanine, cytosine, and thymine- in a strand of DNA
Compare the similarities and differences between meiosis and mitosis
similarities-
both involve DNA replication
differences
- number of chromosomes is halved in meiosis
- meiosis has 2 divisions
- during meiosis crossing over takes place which results in genetic variation
Cloning
The process of producing similar populations of genetically identical individuals.
somatic vs germline cells
Somatic cells are cells whose genetic material cannot be passed on to future generations of people.
Germline cells (or germ cells) are cells whose genetic information may be passed down to future generations of people if they resulted in a pregnancy that came to term.
Independent assortment
states that the alleles of two (or more) different genes get sorted into gametes independently of one another.
In other words, the allele a gamete receives for one gene does not influence the allele received for another gene.
Non-disjunction
Nondisjunction is the failure of homologous chromosomes or sister chromatids to separate properly during cell division.
Apoptosis
Apoptosis is an orderly process in which the cell’s contents are packaged into small packets of membrane for “garbage collection” by immune cells. Apoptosis removes cells during development, eliminates potentially cancerous and virus-infected cells, and maintains balance in the body.
advantages and disadvantages of sexual reproduction
adv:
- produces genetic variation in the offspring
- the species can adapt to new environments due to variation, which gives them a survival advantage
- a disease is less likely to affect all the individuals in a population
disadv:
- time and energy are needed to find a mate
- it is not possible for an isolated individual to reproduce
Karyotype
the number and visual appearance of the chromosomes in the cell nuclei of an organism.
