Biology unit 2 Flashcards
what is deoxyribonucleic acid
DNA molecules
what are chromosomes
strands of DNA, usually arranged in pairs in the nucleus of each cell
what does cytosine pair with
guanine
what is an allele
the form of a gene
what does double helix mean
2 strands of genes in a spiral shape
what does the triplet code determine
which amino acid is next linked (by a chemical bond) in the protein chain
DNA has a ladder-like structure, it is made of 2 long chains of alternating _____ and ________ molecules
sugar and phosphate
what are the 4 different bases that make up DNA
Adenine
Thymine
Cytosine
Guanine
what does adenine pair with
thymine
what does thymine pair with
adenine
what does guanine pair with
cytosine
where does protein synthesis take place
in the cytoplasm
who discovered genetic profiling
Alec Jeffries in 1984
what are gametes
sex cells
what are the gametes of humans called
sperm and egg
what is a diploid
a full chromosome set (body cell)
what is a haploid
gametes containing half chromosome number
give 2 examples where DNA analysis is used
paternity testing, identifying suspects in crime cases
what is a genotype
set of alleles an individual has that determines a characteristic
who discovered inheritance
Gregor Mendel in the 1800’s
what is a gamete
sex cells
what are the human gametes
sperm and egg
why do gametes only contain half of the genetic information needed to form a new individual
so, when fertilisation takes place, they contain the correct number of chromosomes
what is a gene
a section of dna that codes to make a particular protein
what is an allele
different form/version of the gene
what is a phenotype
the appearance of an organism as a result of its genotype/genes
what is heterozygous
an individual that has two different alleles for a characteristic
what is dna
the chemical that forms genes
what is homozygous
an individual that has two of the same alleles for a characteristic
what is a dominant gene
only 1 of these alleles is needed for the characteristic to be shown
what is a recessive gene
two of these alleles are needed for the characteristic to be shown
what is a chromosome
a structure containing genes
describe some ways in which humans may vary
eye colour, hair colour, height
what are the two main causes of variation
genetic and environmental
what lifestyle choices/factors might be responsible for causing environmental variation between individuals
diet, climate, habitat, diseases, culture
what is continuous variation
every individual has the characteristic, but it differs for each individual
what is discontinuous variation
every individual either has the characteristic or they do not
example of continuous variation
height, weight
example of discontinuous variation
tongue rolling, attached ear lobes
how is continuous variation shown on a graph
bar graph with bars touching and a bell-shaped curve
how is discontinuous variation shown on a graph
bar graph with bars separated, shown as discrete groups
define the word clone
genetically identical
what is ionising radiation
high frequency radiation that damages dna
what are liposomes
tiny bubbles within a spray used in gene therapy. they act as a vector to transmit the normal genes into the body
name 2 advantages of gm plants
- pest/disesease resistant crops so higher yields
- medicine can be made by gm organisms e.g insulin
name 2 disadvantages of gm plants
- superweeds may be created if pollen from gm crops is spread to non gm plants
- unknown effects of eating new protein produced in gm crops
what is mitosis
cell division where each division produces 2 daughter cells which have the same number of chromosomes (diploid) and are genetically identical to the mother cell.
what does mitosis do
allows organisms to grow, replace worn out cells and repair damaged tissues
what does meiosis do
produces gametes (sex cells)
what is meiosis
produces 4 daughter cells in every division which have half the number of chromosomes (haploid) and are genetically different to the mother cell
what are stem cells
undifferentiated cells which have the ability to develop into different types of specialised cell
where are stem cells found in plants
in the tip of the roots and shoot
where are stem cells found in animals
bone marrow (adult stem cell)
embryos (embryonic stem cells)
name 2 problems of using embryonic stem cells
there are ethical issues as to if it is a destruction of life
potential rejection from the body as it is not their own cells
name 2-4 advantages of adult stem cells
no rejection (if own cells)
no need to find a donor
no destruction of life (not as controversial)
no need for tissue typing
give 3 examples of specialised cells
muscle cells
nerve cells
blood cells
name 3 sources of tissue stem cells
adult or foetal tissue e.g bone marrow
umbilical cord blood
aborted foetuses
name 2 current stem cell therapies
bone marrow transplants
skin grafting
what is interspecific competition
competition with other species
what is intraspecific competition
competition between same species
what are the physical properties of a gene
sequence of bases in the dna
what are the functional properties of a gene
the protein it makes
the role that the protein has
if the sense organ is the eye then what is the stimulus
light
if the sense organ is the ear then what is the stimuli
sound/gravity
if the sense organ is the nose then what is the stimulus
chemicals
if the sense organ is the tongue then what is the stimulus
chemicals
if the sense organ is the skin then what are the stimuli
pressure, temperature, texture
if the sense organ is the eye then what is the sense
sight
if the sense organ is the ear then what is the sense
hearing/balance
if the sense organ is the nose then what is the sense
smell
if the sense organ is the tongue then what is the sense
taste
if the sense organ is the skin then what is the sense
touch
sense organs are groups of …………… cells
receptor
sense organs respond to stimuli and relay information as ……………. signals called ………. ………….. to the brain
electrical
nerve impluses
the central nervous system consists of the ……….. and the …………. ………..
brain
spinal cord
what is the receptor
the change that is detected e.g a ball moving towards you
what is the receptor
the cells that detect the change e.g light sensitive cells in the retina
what neurones transmit information from the receptor to the co-Ordinator
sensory neurones
what neurones transmit information from the co-Ordinator to the effector
motor neurones
what is the co-Ordinator
this organises the information (brain/spinal cord)
what is the effector
causes the body to do something (muscle or gland) e.g muscles contract
what is the response
what the body does e.g catch the ball
what is a reflex
a fast, automatic reponse to stimulus that protects the body from harm
name 2 features of a reflex action
very fast
automatic
why do we have reflexes
to protect the body from harm
name a type of reflex
withdrawal reflexes e.g touching a hot or sharp object, for protection
what is a reflex arc
the pathway that messages follow in a reflex
what are the 3 neurones involved in the reflex arc
sensory
relay
motor
what is the synapse
a small gap between each neurone which release special chemicals called neurotransmitters to carry messages across the gap
what process helps neurotransmitters carry messages across gaps in-between neurones
diffusion
