Blueprint of Life Flashcards

Question

Explain the relationships between dominant and recessive alleles and genotype using examples

Answer 1

Dominant alleles→ Form of gene expressed in heterozygous condition, masking the other (recessive) form of same gene. Written in UPPERCASE letters. E.g. T Recessive alleles→ Form of gene expressed in homozygous condition. Written in lowercase letters. E.g. t

Answer 2

Paper only presented to small group; work suddenly appeared (may not have been noticed) Work radically different to previous; may not have been understood and little known about cels He wasn’t recognised scientist; more likely to have been noticed if was serious scientist

Answer 3

Sea urchin egg experiment→ behaviour of cell nucleus and chromosomes (in meiosis and fertilisation) Already known→ organisms has set number of chromosomes and in fertilisation (egg and sperm fuse) Found nucleus of egg and sperm contribute 50% of chromosomes to zygote Experiments: Egg and sperm fuse; resulting offspring have characteristics of parents. If only one parent nucleus; abnormalities→ showed that complete set of chromosomes needed for normal; inheritance factors on chromosomes in nucleus

Answer 4

Meiosis of grasshopper cells→ observed chromosomes occur in visible pairs in meiosis (paternal and maternal) During meiosis; chromosome number is halved, chromosome in each pair separate; gamete receives one chromosome from each pair→ fertilisation resotes full number in zygote Concluded that: Chromosomes carriers of hereditary units;arrange themselves independently in middle of cell before divides Chromosomes units involved in inheritance; believed that several Mendelian factors present in one chromosomes; therefore inherited as unit

Answer 5

Before→ Hereditary factors found in nucleus and cytoplasm; After→ Nucleus only Before→ Proteins store hereditary info. After→ full set of paired chromosomes Before→ gametes transport factors to pass onto next generation. After→ random assortment during meiosis Before→ Chromosomes believed to disappear and reappear. After→ Occur in set numbers, in pairs

Answer 6

Chromosome→ made of DNA, proteins Proteins→ histone proteins bind to DNA to form chromatin (in nucleus) DNA→ Double helix structure, basic building block of nucleotide (base, sugar, phosphate) 4 bases; Adenine (A) and Thymine (T), Cytosine (C ) and Guanine (G) NUCLEOTIDE 2 nucleotides linked by covalent bonds between sugar and phosphate DNA tightly wrapped around histone→ protect from damage, allow long DNA length to be packaged so it doesn't move around cell in cell division

Answer 7

DNA contains info in specific sequence of nucleotides (sugar, phosphate, base) Spiral double helix (rungs of ladder→ hydrogen bonds linking (A,T) and (C,G)

Answer 8

Radishes grown in 2 petri dishes; one kept in light. Other kept in dark In dark: grew taller faster; but had yellow leaves → In light: shorter height Radishes in dark moved into light→ leaves became green; gene undamaged, but not expressed in dark

Answer 9

In meiosis; genetic variation from crossing over, random segregation, independent assortment Meiosis; One cell (2 divisions) → 4 haploid cells (genes in each; new combo of parent genes) Independent assortment; paternal and maternal chromosomes sort out independently of one another Maternal don’t all move into one gamete and paternal into another→ random where it ends up→ mixes paternal and maternal (genetic variation) Chromosomes in pair separate→ ensures chromosomes number in gametes is half of original

Answer 10

Variability→ Different forms of a gene within a population (from genes, environment or both) Sexual reproduction increases variability→ increasing gene recombination Greater variability improves pop’s ability to adapt to changes in environment Meiosis and fertilisation→ when gametes form, cross over, random segregation→ results in genetic recombination of paternal and maternal genes within each gamete

Answer 11

Mendelian ratios→ only when similar conditions to Mendel; if genes don’t assort independently,or show dependence→ Mendel's ratios not obtained Cells; 23 chromosome pairs (22 x autosomes, 1x sex chromosomes) Female genotype XX, Male; XY Offspring;equal chance of male or female; determined during meiosis; transfer 1 sex chromosome to each gamete; fusion of gametes in fertilisation Meiosis; Females (44 autosomes plus XX) → halved egg gets 22 autosomes and X. Males→ Half get 22 autosomes and X, half get 22 autosomes and Y X from mother and father→ will be female (XX) X from mum, Y from dad→ will be male (XY) Mendel's experiments; no sex-specific effects; sex-linked inheritance is deviation from Mendel's ratios

Answer 12

At time; Unknown why number of traits that separate in meiosis exceeds number of chromosomes Sutton/Boveri→ more than one trait is present on each chromosomes (didn’t demonstrate) 1910→ Morgan experiments on gene eye colour in fruit flies; located on X chromosome→ heredity factors exchanged between X chromosomes Drosophila Melanogaster (normally red eyes, but found mutant white eyed male) → crossed to see if white eyed gene would show Mendel ratio

Answer 13

CROSS 1 Pure bred parents o obtain F1 hybrid offspring White eyed male and red eyed female CROSS 2 Crossed F1 hybrid offspring to obtain F2 generation Expecting Mendelian 3:1 ratio but more than 80% had red eyes and less than 20% white eyes Most white eyed were male. Thought females couldn’t have white eyes CROSS 3 Typical cross to investigate hypothesis → crossed white eyed male with heterozygous red eyed female Results shown in F2 generation,both males and females had white eyes Next (and correct) hypothesis→ white eyed characteristic is ‘sex-limited’. Genetic crosses proved red eyes were sex limited (carried on sex chromosome)

Answer 14

Doesn’t show Mendelian pattern (pairs of alleles don’t show dominance over the other) Heterozygote where 2 different alleles for same gene; both expressed separate (both dominant) E.g. Cattle have red or white→ Heterozygous may have red and white coat→ roan (not in patches but interspaced red and white hairs)

Answer 15

Genotype + environment= phenotype E.g. (TT)plant may end up same size as (tt), if grew in unfavourable conditions (lack of water) E.g. Temp can affect phenotype of animals: or effect of soil pH on colour of hydrangea flowers; Pink flowers in alkaline or blue flowers in acidic Identical twin; differences due to environmental rather than genetics→ One may have freckles (sun exposure) other may not Environmental factors influencing humans; smoking, physical activity levels, diet, nutrition

Answer 16

DNA replication→ DNA copied; produce new molecules with same base sequence STAGE 1: DNA double helix unwound, separated into strands (hydrogen bonds broken) STAGE 2: Strands act as templates→ Nucleotides and bases form bonds with bases on parent strand STAGE 3: Daughter DNA molecules rewind in double helix; identical in base sequence to parent (due to complementary base pairing) Each of new strands is complementary to template it was made on and identical to other template

Answer 17

Polypeptide synthesis; uses RNA→ single stranded nucleic acid (bases A, C, G and Uracil→ replaces Thymine; T) Three types of RNA: mRNA (messenger RNA) tRNA (Transfer RNA) and rRNA (ribosomal RNA) DNA to polypeptide; DNA code determines amino acid sequencing in polypeptide chain→ DNA info transcribed to mRNA from template strand 3 nucleotides on mRNA→ codon for particular amino acid

Answer 18

Copy of gene is made (RNA not DNA) → carries info for making polypeptide (mRNA) Double helix unwinds; RNA nucleotides assemble use one DNA strand as template; mRNA separates from DNA and double helix reforms

Answer 19

Ribosomes move along mRNA molecule→ transfer RNA molecules present around ribosomes (bind to them→ only bind to anticodon that is complementary to codon on mRNA) Codon and anticodon base link (form hydrogen bonds) tRNA molecules carry amino acids→ bonded by peptide linking; dipeptide formed→ upper tRNA detaches, another one binds→ chain of 3 amino acids forms These stages are repeated until a polypeptide is formed

Answer 20

1941→ mutants of fungus→ led to discovery of genes provide instructions for making proteins Hypothesis; gene controls production of one enzyme→ evidence needed Designed experiment to attempt to mutate genes of mould→ evidence led to hypotheses; genes affect enzyme productivity→ Breakthrough! (At time; ongoing debate; heredity material protein or DNA?) EXPERIMENT: Irradiated bread mould with X-rays (induce mutations) → showed some mutants no longer produced amino acid (implies particular enzyme no longer functions) Tested; If loss of function had genetic basis→ crossed mutant with normal mould; found offspring shared mutant phenotype→ inability to produce amino acid is inherited (due to mutation) Found different enzymes in different mutants altered or missing; proved gene determines structure of enzyme→ proposed one gene-one enzyme hypothesis Changed to one-gene-one protein when demonstrated other proteins besides enzymes encoded by gene Found one gene not necessarily responsible for structure of entire protein; but for each polypeptide chain making up protein (currently accepted)

Answer 21

Proteins: Amino acid chain joined by peptide bonds; may be from many polypeptide subunits Polypeptide: Molecule consisting of many joined amino acids→ aa joined by peptide bonds To make particular polypeptide, amino acids must be linked up in a precise sequence Genes store info needed for making polypeptides→ info is stored in coded form Precise sequence of bases in gene codes for the sequence of amino acids in a polypeptide

Answer 22

Mutagens are environmental agents that cause mutations; Chemical (asbestos), Biological (HIV), Mutagenic radiation (UV, nuclear reaction) Changes to genetic material arise during DNA replication Mutations alter genes; change nucleotide sequence in DNA→ One or more genes may be altered from original form (Allele 1, Allele 2) 2 variations of gene is formed→ new allele formed One or more genes may be altered from original. E.g, Allele 1→ altered polypeptide→ new protein Most new proteins have little effect on organism, but some lead to genetic disorders, inherited diseases Effect of new proteins on next generation: If mutation in a somatic cell→ individual may be affected but no effect on future generations If mutation is in germline cell (gametic mutation) → alleles can be inherited and have significant effects on population→ result in evolution Changes to genetic material arise during DNA replication→ result in Change to single gene (gene mutation) or rearrangement of blocks of whole chromosomes (chromosomal mutations)

Answer 23

During late 1800’s and early 1900’s, many scientists were involved in studying radiation Harmful effects of radiation were unknown→ scientists such as Marie Curie who were exposed to large amounts of radiation over a prolonged periods of time, developed various illnesses Marie Curie worked with ionising radiation for most of career; died from leukemia (overexposure) Survivors of Hiroshima bomb→ suffer physical mutations (radioactive output of nuclear explosion)

Answer 24

Mutation; basic source of variation Mutations affect base sequence of DNA→ understand how can be passed from one generation to next→ supports Darwin’s theory of evolution (Explains how heritable variation arises) Mutation will result in change in phenotype, may not do anything, or may confer advantages disadvantage to organism Mutations provide diversity of genetic material that results in variation in phenotype If mutations can be inherited→ provide variation on which natural selection acts Evolutionary purposes, mutation can be redefined as heritable change in genetic material

Answer 25

Majority of mutations; detrimental to or have no significant effect on environment; some beneficial Some organisms→ developed resistance; most killed, some naturally resistant survive and reproduce (pass genes→ resistant pop develops) E.g. Sheep blowfly lay eggs in wet wool; burrow into skin→ loss of production → developing resistant to agricultural insecticides If insecticides rotate, effectiveness increased

Answer 26

Many bacterial infections treated with antibiotics. Interfere with protein synthesis Many bacteria become resistant to wide range of antibiotics Animals given antibiotics to grow faster and not have disease→ if humans eat or drink milk from animals, then resistant bacteria could be transferred to humans Encouragement of doctors to restrict general use of some selected antibiotics

Answer 27

Theory; Evolution occurs in short bursts of rapid change, followed by longer periods of stability If evolutional change is gradual, could be predicted; fossilised remains showing these ongoing changes Darwinists use traditional forms to support perspective of gradualism→ gradual change over an extremely long period of time Many fossilised remains show millions of years with no noticeable evolutionary change to species E.g. Soft bodied organisms dominates seas for hundred of millions of years and in period of million years disappeared and were replaced by organisms with shells and skeletons Supporters of punctuated equilibrium argue if evolution occurs gradually, as proposed by Darwinists there should be greater diversity among living organisms that exist Fossil records is incomplete so difficult to come to an agreement on evolutionary change

Answer 28

Scientists associated with double helix discovery; Rosalind given no recognition Franklin; find out structure of DNA molecule (X-ray crystallography) → Identified A and B form Work provided without knowledge or consent to Cambridge competitors through Wilkins; used her data to build model Maurice Wilkins→ studied diffraction images and discovery of patterns to guess molecular DNA structure Wilkins, Franklin diffraction images→ discovery of 3D helical nature Crick and Watson analyse Franklin/Watson crystallography; realised DNA structure was helix Processed info from other, manipulated model→ Watson and Crick discovered fmoud double helix Watson, Crick and Wilkins won Nobel Prize (1962) for work in DNA→ Franklin wasn’t honoured and appropriately acknowledged→ already dead

Answer 29

Sperm taken from chosen male; inserted into selected females Cost effective; frozen sperm transported; not animals(reduce injury danger) Sire several offspring with different females; conservation of species→ but reduces genetic diversity Bred selectively; alleles increase in gene pool selected by breeder not nature Survival and reproduction in pop→ depends on alleles that are useful to humans, not environment

Answer 30

Remove stamens; dust pollen onto stigmas of another flower or same flower; E.g. Mendel pea plants Greater degree over breeding process; ensures pure breeding→ but less genetic diversity; species vulnerable to sudden environment change

Answer 31

Reproductive cloning: Genetically identical fully developed organism using cell from other organisms Therapeutic cloning: Cells from individual to produce cloned early embryo Gene cloning: Producing identical copies of a gene E.g. Dolly the sheep, Bananas, twins Characteristics can be precisely bred→ conservation; reintroduce extinct genes, endangered animals Reduces genetic diversity; increases risk of being wiped out from sudden environmental change Not natural→ need to ‘switch on” genes and most experiments fail Organisms; genetically identical→ reduced variability

Answer 32

Somatic Cell Nuclear Transfer→ SCNT→ 3 animals; nucleus donor, egg donor, surrogate mother Somatic cell nucleus transferred to egg without nucleus; reprogrammed to become zygote and grows E.g. Dolly the sheep; cell from 6 yr old ewe udder→ injected into enucleated second sheep cell; fused with electricity→ grow and develop normally→ injected into third sheep uterus Sheep born dentic twin to sheep donating egg

Answer 33

A species that has genes transferred into its genetic code from another species

Answer 34

EXAMPLE: Gene from bacteria has been transferred to cotton called BT cotton→ Gene codes for bacterial protein called BT toxin that kills Helicoverpa moth→ major pest of cotton crop REASONS FOR USE: Use of less insecticide on BT cotton crop→ benefits farm workers and wildlife Increase in crop yield

Answer 35

DNA and proteins of transgenic organisms unlikely to cause any problems as digested in human gut Research suggests transgenic species don’t survive long in natural ecosystems and if genes transfer to wild species, natural selection acts against them Transgenic techniques will reduce cost of food production, which benefits producer and consumer Transfer of genes between species is natural phenomenon.

Answer 36

Impossible to be certain about long-term health effects of genes in GMO foods or proteins made using genes Genes could escape and be transferred to wild plants or animals. E.g. Possibly creating superweeds Will allow multinational companies that develop them to become too powerful Infringement of rights of every species to independently exists and could cause suffering in animals

Answer 37

DNA can be introduced directly into an animal cell by microinjection Multiple copies of desired transgene are injected via a glass micropipette into a recently fertilised egg cell→ then transferred to surrogate mother Not efficient; many don’t survive

Answer 38

Foreign DNA into living tissues literally shoots directly into organism using “gene gun” Microscopic particles of gold or tungsten are coated in DNA and propelled by burst of helium into skin and organs of animals and tissues of intact plants Some of cells express introduced DNA as if it were their own.

Answer 39

Messenger RNA coding for insulin is extracted from human pancreas cells that make insulin DNA copies of messenger RNA made and sticky ends are made by adding extra G nucleotides to gene ends Plasmids are small loops of DNA found in bacteria→ cut open using restriction enzymes and sticky ends made by adding C nucleotides at ends of cut plasmid Insulin gene and plasmid are mixed. Link by complementary base pairing (G-C) between sticky ends Plasmid with human insulin gene inserted is called recombinant plasmid Suitable host cell is chosen to receive gene. E.g. E. Coli bacteria Recombinant plasmid are mixed with host cells.Host cells absorb them Genetically modified E. Coli are cultured in fermenter E. coli bacteria start to make human insulin which is extracted, purified and used by diabetics.

Answer 40

Decreased genetic diversity;only one parent; identical to one parent Desired characteristics evident;individual control and reproduced in short time All identical→ less likely to survive sudden environmental change, foreign pathogens May be used in conservation with endangered or extinct animals

Blueprint of Life Flashcards

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