Reproduction and Inheritance Flashcards
what are chromosomes?
long lengths of DNA coiled up
what are genes?
what do they do?
sections of DNA
chemical ‘instructions’ for making an organism
codes how to make particular proteins
proteins determine inherited characteristics
two copies, one from each parent
where are chromosomes found ?
In the nucleus
Human cells are which? haploid/diploid
diploid
what is a diploid cell?
has two sets of chromosomes (in pairs)
what is an allele ?
different versions of the same gene
(eye colour) (hair colour)
can be recessive or dominant
what is a dominant allele?
allele characteristic develops only if allele is present on one or both chromosomes in a pair Capital letter (C)
what is a recessive allele?
allele characteristic only develops if allele is present on both chromosomes in a pair small letter (c)
what is homozygous ?
identical alleles in a gene
CC or cc
what is hetrozygous ?
two different alleles in a gene
Cc
what is the Genotype ?
the alleles you have
what is the Phenotype ?
the characteristics the alleles produce
what is Mono hybrid cross ?
breeding two organisms to look at one characteristic
what is the phenotypic ratio ?
ratio of different ratios in punnet square
what is a condominant allele?
example?
neither allele is recessive so characteristics shown from both alleles
e.g. not blood group A or B, but AB
what is DNA?
how is it held together?
strands coiled together in a double helix
strands held together by chemical bases A C G T
bases are paired, always A-T and C-G, called complementary base-paring
DNA is a nucleic acid
what are the Bases names for A T C G?
adenine
cytosine
guanine
thymine
what is asexual reproduction ?
involves only one parent. The offspring have identical genes to the parent - so there’s no variation between parent and offspring
Asexual reproduction is mitosis/meiosis
mitosis
what is mitosis ?
where does it take place?
cell reproduces itself by splitting to form 2 cells with identical sets of chromosomes (identical genetic info)
takes place everywhere
what are the uses for mitosis ?
asexual reproduction
growth and repair
cloning
The two different ways plants reproduce asexually
Growing new plants from its stem
Cloning
describe how strawberry plants asexually reproduce
Parent strawberry plant send out runners (fast growing stems) above ground
Runners take root at various points
New plants are clones so no genetic variation
what is sexual reproduction ?
fusion of male and female gametes to produce genetically different offspring, because there are two parents, offspring contain mixture of parent’s genes
what is the Male (human) gamete
sperm cell
what is the Female (human) gamete
egg cell
human gametes are diploid/haploid …
how many chromosomes does each have?
haploid meaning they have half as normal cell
23 chromosomes each
define human fertilisation
fusion of male and female gamete to form a zygote
zygote has full set of chromosomes (diploid)
human sexual reproduction - what is the process after zygote formed to embryo ?
zygote undergoes cell division (by mitosis) and develops into an embryo
what is meiosis ?
where does it happen?
cell division, produces 4 haploid cells whose chromosomes are not identical
only happens in reproductive organs for humans
what is the stamen ?
plant male reproductive part
consists of anther and filament
what is the anther ?
contains pollen grains which produce male gametes
what is the filament ?
stalk that supports the anther
what is the carpel ?
female plant reproductive part
consists of ovary, style and stigma
what is the stigma ?
end bit that pollen grains attach to
what is the style ?
rod-like section that supports stigma
what is the ovary ?
contains female gametes inside ovules
what is pollination ?
transfer of pollen from anther to stigma, so that male gametes can fertilise female gametes in sexual reproduction
what is cross - pollination ?
type of sexual reproduction where pollen is transferred from one plant to the stigma of another
cross-pollinating plants rely on insects/wind
how are plants adapted for insect pollination ?
brightly colour petals to attract insects
scented flowers and nectarines
sticky pollen grains which stick to insects
stigma also sticky so pollen sticks on it
what are nectarines ?
glands in plant which secrete nectar
how are plants adapted for wind pollination ?
small dull petals - no need to attract
no nectarines / scents needed
lots of small / light pollen grains
long filaments that hang anthers outside to release pollen
large feathery stigma outside to catch pollen
how does plant fertilisation happen?
pollen lands on stigma - pollen tube grows out of pollen into ovule - nucleus from male gamete moves down to join female gamete - fertilisation occurs to form zygote - zygote uses to mitosis to form embryo - each fertilised female gamete forms seed - ovary develops into fruit around seed
define fertilisation
fusion on gametes to form zygote
what are the conditions needed for germination ?
why are these needed?
water - activate enzymes to break down food reserves
oxygen - for respiration, provides energy for growth
suitable temp - optimum temp for enzymes (depends on type of seed)
how does a germinating seed get energy ?
what is the energy needed for?
seed contains embryo and food reserves wrapped in hard seed coat
uses glucose for respiration for energy to grow
once leaves develop, it can photosynthesise
explain how you can artificially clone a plant
why is this effective?
can take cuttings from good plants and plant them to produce genetically identical clones
these plants can be produced fast and cheap
what is the urethra ?
tube which carries sperm through penis during ejaculation. Also urine passes through here
what is the erectile tissue ?
swells when filled with blood to make penis erect
what is the testis (plural testes)?
where sperm is made
what is the glands ?
produce liquid that’s added to sperm to make semen
what is the sperm duct ?
muscular tube that carries sperm from testis towards urethra
what is the scrotal sac ?
hangs behind penis and contains testes
how often is an ovum (egg) produced?
every 28 days
what if an egg doesn’t get fertilised?
ovum breaks up, and pass out of vagina
what if an egg does get fertilised?
ovum starts to divide, new cells travel down Fallopian tube to uterus and attach to uterus lining, develops into embryo
what does ovum mean?
egg
what is the Fallopian tube (oviduct)?
muscular tube that carries ovum from ovary to uterus
what is the ovary ?
organ that produces eggs (ova) and sex hormones
what is the uterus (womb)?
organ where embryo grows
what is the vagina ?
where sperm is deposited
what is the cervix ?
neck of the uterus
what is the uterus lining ?
has good blood supply for implantation of embryo
what are the female secondary characteristics and hormone ?
oestrogen causes : extra body hair hips widen development of breasts ovum release and start of periods
what are the male secondary characteristics and hormone ?
testosterone causes : extra body / facial hair muscles develop penis and testicles enlarge sperm production deepening of the voice
what is the stage 1 of menstrual cycle ?
bleeding starts
uterus lining breaks down for about 4 days
what is the stage 2 of menstrual cycle ?
uterus lining builds up again from day 4 to 14, into think spongy layer of blood vessels, ready to receive fertilised egg
what is the stage 3 of menstrual cycle ?
an ovum develops and is released from the ovary at day 14
what is the stage 4 of menstrual cycle ?
walls is then maintained for about 14 days until day 28.
If no fertilised egg lands, uterus lining breaks down
what is oestrogen for? (menstrual cycle)
when is it produced?
causes uterus lining to thicken and grow
stimulates (production of LH to) release of an ovum at day 14
what is progesterone for? (menstrual cycle)
when is it produced?
maintains uterus lining
when progesterone levels fall, uterus lining breaks down
if becomes pregnant, levels stay high
what is the function of the placenta ?
provides developing baby with nutrients / oxygen
takes away waste
what is the function of the amniotic sac?
full of amniotic fluid which surround embryo to protect it
what is the 23rd chromosome labelled ?
XX or XY
what causes male characteristics ?
The Y chromosome causes males (so XY)
what causes female characteristics ?
XX chromosomes
what causes genetic variation ?
Sexual reproduction and mutation in genes
List some variation factors which aren’t affect by the environment
eye colour
hair colour
inherited disorders (cystic fibrosis)
blood group
How can the environment affect height / weight ?
the diet - so poor diet leads to stunting growth
List the variation factors of plants
sunlight / moisture level / temp / mineral content of soil
The environment greatly affects plants
State the theory of evolution
Life began as simple organisms from which more complex organisms evolved
what is a mutation ?
describe how they work
a random change in DNA
changes sequence of DNA bases, changing the production of protein, which could lead to new characteristics, increasing variation
Explain how a mutation can happen spontaneously
this happens when a chromosome doesn’t quite copy itself properly
How can you increase chances of a spontaneous mutation ?
ionising radiation - X-rays / gamma rays …
chemicals called mutagens - like in tobacco
Give the answer for a 5 mark what is natural selection question
genetic mutations in an organism lead to variation
variation can lead to specific organisms surviving
organisms go onto to reproduce and pas on their genes to their offspring
happens over several generations
how can mutations be harmful ?
if occurs in reproductive cell, offspring might develop abnormally or die
if occurs in body cell, mutant cell may multiply and invade parts of body (cancer)
explain how antibiotic-resistant bacteria come about and how they are a problem
random mutations in DNA causes them to resist antibiotics, so live longer and reproduces, passing on resistant gene
problem because they are much harder to get rid of
