Level 1 Biology Flashcards
what is the smallest unit of life which is invisible to the naked eye?
the cell
what does a cell contain within it?
a nucleus
what is the nucleus’s make up?
it is a dense double membraned organelle which contains the genetic material (DNA)
what does DNA stand for?
Deoxyribonucleic Acid
how are base pairs held together?
with hydrogen bonds
what makes up a nucleotide?
a sugar and phosphate molecule
where do the the sugar and phosphate molecules come from?
they are taken from the food we eat and it strengthens them and helps to link the bases to others
what is each strand made up of?
a big chain of specific nucleotides
what is a gene?
it is a length of DNA which codes for a particular characteristic (hair)
what is an allele?
it is an variation of the gene (red hair)
how many sets of chromosomes are in a cell?
two sets, one from each parent
what are all of the genes in an organism called?
a genome
what is a trait?
it is a feature of an organism that varies between organisms
what does one gene equal?
one characteristic
where are genes found?
in chromosomes
what contains specific genes?
chromosomes
how long is DNA?
5 billion bases long
what is DNA organised into?
into triplets ( a series of 3 bases)
what does each triplet code for?
it codes for an amino acid
what is amino acid?
it is the building block of proteins, you need a lot of it to make something
what does the order of triplets determine?
it determines the order of amino acids (the proteins being made)
how many types of amino acids are there? does the order of the triplets mean for amino acids?
there are 20 types of amino acids and the order of the triplets creates the different amino acids
what is the structure of DNA?
a twisted double helix
what bases make up DNA? and what bases pair up?
A+T G+C
what happens when a cell copies itself?
it winds its DNA up into tight structures called chromosomes
how many chromosomes are in an organism?
there are 23 pairs so 46 chromosomes
what is a diploid cell?
it is a cell with 46 chromosomes
what do chromosomes do?
they provide instructions for the cell to carry out specific roles
what is a genotype?
it is the coding for the phenotype
what is a phenotype?
it is the physical characteristics which is the out come of the genotype
what is homozygous?
it is when the genotype has either the same uppercase/lowercase genotype e.g. RR or rr
what is heterozygous?
it is when the genotype is a combo of upper and lowercase e.g Rr
when do recessive alleles express themselves
they have to be homozygous recessive to present
how many autosomal chromosomes does a human have?
22
what happens if cells that make the sperm and the egg don’t divide properly?
Mutations occur and can result in less chromosomes
at what level do mutations occur?
gene or chromosome level
what is mutation?
a permanent change to the genetic code / base sequence in DNA
what does mutations lead to?
a change in characteristics
when can mutations occur?
during DNA replication before the cell divides
how do mutations to occur?
they happen naturally but the rate can be increased by mutagens
when cant mutations be passed down?
in normal body cells called somatic
when can mutations be passed down?
when the mutation occurs during gamete creation they become inheritable
what is asexual reproduction?
it the production of offspring which is genetically identical to its only parent
what plant is classified as a tuber?
potato - the large stem stores excess glucose which means that it can grow more shoots, roots, absorb water and photosynthesise
what plant is classified as a runner?
Strawberries - they are able to spread across surfaces easily and reproduce quickly
why is genetic variation important?
because it enables the species to survive changes in habitats
how do organisms get characteristics?
they can be inherited from parents (black hair) and they can also be non - inheritable (permed hair)
what is pure breeding?
it is when an organism is breed for a specific characteristic that has the genotype which is homozygous dominant or recessive
what is natural selection?
it is when select organisms have certain phenotypes which allows them to survive new changes to the environment or adaptations
why is natural selection important?
because it will leave the ones which have survived due to them adapting so in turn they will breed within their population to enhance the whole species survival
what is independent assortment?
it is when different genes within gametes which get sorted randomly/ independently
during independent assortment what happens ?
the alleles that a gamete receives for one gene doesn’t influence the others
what is crossing over?
it is the exchange of chromosomes segments between homologous chromosomes
when does crossing over occur?
during meiosis
what is the result of crossing over?
a new combo of genes which produces a unique organism
what is a test cross?
it is w way to find possible genotypes for an unknown individual with a known homozygous recessive allele
what is a test cross used to find?
to find whether a dominant phenotype is homozygous or heterozygous
what happens if the unknown parent is homozygous dominant? - test cross
all of it’s off spring will express the dominant phenotype
what happens if the unknown parent is heterozygous ? - test cross
half of the off spring should be dominant and half recessive
what is discontinuous varitaion?
it is individuals who’s features cant be measured across a range it is put into a specific category like blood type
what is discontinuous variation controlled by?
it is controlled by alleles of a single gene - the environment has no impact on it
what is continuous variation?
it is a complete range of measurements which can’t be put into a category specifically like weight or height
what is continuous variation controlled by?
it is controlled by alleles but can be influenced by environmental factors
what are the sources of variation?
mutation, sexual reproduction and fertilisation
environment
what is meiosis?
it is the cell division which creates sex cells called gametes
how many chromosomes does daughter cells contain during meiosis?
they contain half the amount of chromosomes from the parent cell
how many daughter cells are created during meiosis?
four daughter cells are created
where does meiosis occur?
in mature organisms - mammals, ovaries and testies - plants, stamens and ovules
what is formed from meiosis cell division?
two daughter cells which are genetically different from each other
what are the steps in meiosis? and what is the acronym?
- chromosomes shorten and become viable
- they come together in homologous pairs and then crossing over occurs
- Segregation - spindles form and the chromosome are pulled apart to opposite poles
- each cell splits into two daughter cells
- each daughter cell has the haploid number of chromosomes but each is made of two chromatids
- a new spindle forms and chromosomes are arranged on the equator
- chromatids are separated to the cell ends
- each daughter cell divides into two to finally form four daughter cells with half the chromosomes
CSTHS2SSED
what is mitosis?
it is cell division which creates new cells to heal and for growth
does mitosis involve sperm or egg cells?
no it doesn’t
what does mitosis produce?
identical body cells
what does the cells contain in mitosis?
they hold the nucleus which has the DNA inside
are cells always mitosising?
no they are growing, replicating and functioning
before splitting what is needed - mitosis
all of the extra chromosomes needed
when cells are mitosising and duplicating, how many chromosomes are there?
there are 46 before and after there is 92 chromatids
what is the stages of mitosis known as?
PMAT
what are the phases of mitosis?
prophase - chromosomes condensing and thickining
metaphase - the chromosomes are in the middle
anaphase - the chromosomes are pulled apart to the opposite poles by spindles connected to the centriole
telophase - chromosomes at opposite sides with new nuclei forming on each side
what is cytokinesis?
it is responsible for the separation of the two cells by splitting the cytoplasm
what happens after cytokinesis?
two daughter cells are produced
what is a pedigree chart?
it is like a family tree of genetic info on phenotypes, genetic conditions and trait origins
what is cytoplasm?
it is a gel-like substance which is inside of a cell
