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96 Cards in this Set
- Front
- Back
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What is genetics?
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The study of hereditary traits
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What is DNA?
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the material that codes for all characteristics
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What is a gene?
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A small portion of genetic material that codes for a single characteristic
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What is a chromosome?
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DNA that is tightly wound togehter containing many genes
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What is mitosis?
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cell division which results in two cells which will have identical nuclei (identical chromosomes)
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What is meiosis?
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the form of division that produces cells with half the normal compliment of chromosomes
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What cells does meiosis occur in?
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sex cells only- egg cells and sperm
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Where are chromosomes found?
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inside the nucleus of every body cell
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How many chromosomes do humans have in each cell?
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46 chromosomes - 23 pairs
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What is DNA organised into inside of cells?
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chromosomes
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what do chromosomes control?
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1. all the characteristics in the cell
2. activities/functions of the cell |
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what are chromosomes divided into?
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genes
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what do genes cause?
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the development of certain characteristics
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how are chromosomes arranged in the nucleus?
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chromosomes are organised into pairs
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what percent of DNA comes from each parent?
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50% from each parent
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each pair of chromosomes is a result of....
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chromosomes coming from the male and the female parent
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what position are the chromosomes' genes in?
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the same type of genes are in the same position along the chromosomes
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what is a gamete?
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a sex cell
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how many chromosomes do gametes have?
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half the number of other cells
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how many chromosomes do human gametes have?
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23
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what is the full number of chromosomes?
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the diploid
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what is the half number of chromosomes?
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the haploid
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what is a haploid?
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a single set of unpaired chromosomes
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when and where does mitosis occur?
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in all body cells when they are forming new cells for growth and replacement of dead cells
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what are the eight steps of mitosis?
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1. the cell starts with the diploid number of chromosomes
2. each chromosome replicated (forms an identical chromosome) 3. the pairs of chromosomes (a pair = original + new) are joined together 4. the nuclear membrane disappears 5. the pairs line up along the centre of the cell 6. the pairs of chromosomes split and each one moves to opposite ends of the cell 7. nuclear membranes form around each idenical set of chromosomes 8. the cell divides to form two cells with identical sets of chromosomes (identical nuclei) |
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What is meiosis used for?
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Reproduction only
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What occurs during meiosis?
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Sections of chromosomes break off and swap with other chromosomes when they rejoin
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What happens when chromosomes break off during meiosis?
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genes stay in the same position but on different chromosomes
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What causes variety in sex cells?
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the chromosomes break off and swap with other chromosomes
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how many sex chromosomes does each cell have?
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two
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what are the two types of sex chromosomes?
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X and Y
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Y chromosomes are ...
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deficient in some genes
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X chromosomes are ...
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complete
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what sex chromosomes do females have?
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X and X
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what sex chromosomes do males have?
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X and Y
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why are males more susceptible to sex linked diseases?
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males are deficient in certain genes
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which sex chromosome is shorter?
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Y
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how many sex cells does a gamete have?
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one
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what do karyotypes show?
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the number and appearance of chromosomes in a cell
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how are karyotypes arranged?
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in pairs from the longest (first) to the shortest (pair 22)
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what chromosomes are shown last on karyotypes?
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sex chromosomes
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genotype
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letters used to denote the type of gene present
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phenotype
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the physical characteristics shown in the individual
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gene
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the actual characteristic eg. hair colour
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allele
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the type of gene present on the chromosome
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homozygous
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two alleles that are the same for the same type of gene
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heterozygous
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two alleles that are different for the same type of gene
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dominant genes are shown with a ___ letter
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capital
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recessive genes are shown with a ___ letter
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lowercase
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if both alleles are capitals, the genotype is
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homozygous dominant
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if both alleles are lowercase, the genotype is
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homozygous recessive
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if both alleles are different, the genotype is
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heterozygous
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generalised ratios
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not exact, eg. 29:8 = 3:1
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incomplete dominance
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a gene is not completely dominant over another gene
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example of incomplete dominance
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roan cow
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co-dominance
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offspring shows both of parents' characteristics
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example of co-dominance
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AB blood type
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sex linked disease
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disease which has recessive gene coded for on x chromosome
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why are men prone to some sex link diseases
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there is no gene on the Y chromosome to counteract the X chromosome's gene
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haemophilia
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no enzyme for blood clotting
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nature vs nurture
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differences in organisms because of genes and environment
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nature
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genetic variation that occurs due to genes inherited
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nurture
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how well genes have been expressed due to environmental factors
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DNA
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deoxyribonucleic acid
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nucleotides
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phosphate, sugar, bases
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DNA is made of ___
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chains of nucleotides
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where is DNA found?
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inside chromosomes
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what are the bases A and T
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adenine and thymine
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what are the bases C and G
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cytosine and guanine
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DNA twists to form a ___
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double helix
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mutation
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a change in the genetic code
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two types of mutations
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point and deletion
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point mutation
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bases are removed and replaced
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deletion mutation
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a single base is removed but not replaced
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four causes for mutations
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radiation, x-rays, chemicals, drugs
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codon
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three nucleotides which form a sequence of genetic code
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anti-codon
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corresponding pairs to codons
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amino acids join and form ___
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proteins
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amino acids are formed by
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codons
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after proteins are formed, they
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leave the cell
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proteins are responsible for
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characteristics
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nucleotide
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sugar, phosphate, base
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chromatid
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one of the two strands into which a chromosome divides longitudinally during cell division
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centromere
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the constricted region joining the two sister chromatids that make up a chromosome
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five phases of mitosis
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IPMAT
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mitosis stage one
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interphase
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mitosis stage two
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prophase
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mitosis stage three
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metaphase
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mitosis stage four
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anaphase
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mitosis stage five
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telophase
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interphase
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1. DNA is copied
2. centromeres replicate |
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prophase
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1. chromosomes condense
2. mitotic spindle forms |
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metaphase
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metaphase plate forms
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anaphase
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chromatids seperate
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telophase
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1. chromatids move to opposite ends of the cell
2. daughter nuclei form |
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restriction enzyme
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cuts DNA after a certain base
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