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Flashcards in Reproduction and Inheritance Deck (53)
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how do alleles create differences in inherited characteristics?

alleles can be dominant (represented in genetics by a capital letter) or recessive (represented by a lower case letter) A=dominant a=recessive


what things can mitosis occur during?

1. growth- to create more cells eg. skin cells allowing the body to grow
2. repair- to replace damaged or dead cells
3. cloning- to create replicas of a specific cell
4. asexual reproduction- asexual reproduction means that there is only one parent, so the offspring are identical to that parent


what is the diploid number of chromosomes in human cells?



what is the haploid number of chromosomes?



how many chromosomes do gametes have?

23- so they can fuse with another 23 during fertilisation and produce a zygote


what environments are asexual and sexual reproduction best suited to?

sexual= changing
asexual= stable


what are the roles of testosterone in the development of secondary sexual characteristics?

- production of sperm
- growth of sexual organs
- body hair- pubic, arms, face
- body mass will increase, including muscle mass
- voice breaks
- development of sexual drive


what are the roles of oestrogen in the development of secondary sexual characteristics?

- the beginning of the menstrual cycle
- body mass increases and redistributed- hips/chest
- body hair- pubic
- voice deepens slowly
- development of sexual organs


what does mitosis do?

it produces two new cells that are identical to each other, and to the parent cell


what is found in the nucleus of a cell?

the nucleus of a cell contains genetic material, in the form of chromosomes. Chromosomes are long lengths of DNA coiled up.


what is a gene?

genes are shorter regions of DNA (a section of a molecule of DNA)


what is the purpose of genes?

genes carry the genetic code for a particular characteristic, cell activity or production of a particular protein


what is the meaning of homozygous?

individuals who are homozygous for a certain gene carry two copies of the same allele eg. BB or bb


what is the meaning of heterozygous?

individuals who are heterozygous for a certain gene carry two different alleles eg. Bb or bB


what is a punnet square?


what are the differences between sexual and asexual reproduction?

in sexual reproduction, two parents create non-identical offspring, inheriting characteristics from both parents. In asexual reproduction a single parent creates genetically identical offspring


how is gender determined?

the 23rd chromosome pair is the one that determines whether you are male or female. Every male has 'XY' as his 23rd pair and every female has 'XX'. 50% chance of being male or female


what is the meaning of dominant?

a characteristic which will show up in the offspring even if only one of the alleles is inherited


what is the meaning of recessive?

a characteristic which only shows up in an offspring when both the alleles are inherited


describe the structure and functions of the male reproductive system

- prostate- add fluid to the sperm; this compound is semen
- sex glands- add nutrients to the sperm; this is semen
- sperm duct- sperm travels down this tube to be mixed with nutrients from the glands
- urethra- allows urine and sperm down to exit the body
- testis- produce sperm by meiosis and produce testosterone
- penis- injects sperm into the vagina


how are wind pollinated flowers adapted for pollination?

- small/dull petals as insects don't need to be attracted
- no scents or nectaries
- small, light pollen grains (and lots of them) so they can easily be carried by the wind
- long filaments that hang the anthers outside the flower so that lots of pollen gets blown away
- a big feathery stigma to catch pollen carried past by the wind


how is fruit formed?

1. the pollen grain lands on the stigma of another flower of the correct species
2. pollen tube begins to grow through the style to the ovule
3. nucleus from male gamete of the pollen passes along the pollen tube, then fuses with the nucleus of the ovule (female)
4. this fertilises the ovule, forming the seed (zygote)
5. the ovule wall becomes the seed coat
6. the ovaries become the fruit
7. then comes germination, a process controlled by enzymes


how are insect pollinated flowers adapted for pollination?

- brightly coloured petals to attract insects
- scented flowers and nectaries, to attract insects
- big and sticky pollen grains to easily stick to insects as they fly from plant to plant
- sticky stigma so any pollen picked up from other plants will stick easily


what are the roles of each part of a plant?

- the anther- contains pollen grains (these produce the male gametes)
- the filament- holds up the anther so they are easily reached by insects brushing against them
- the stigma- the sticky bit where the pollen grains attach to
- the style- supports the stigma
- the ovary- contains the female gametes


what is the meaning of codominance?

two alleles which are both expressed in the phenotype of an organism


what is an allele?

an allele is an alternative form of a gene (one member of a pair) that is located at a specific position on a specific chromosome


explain the division of a diploid cell by mitosis?

1. cells get the signal to divide; DNA forms X-shaped chromosomes to duplicate itself
2. chromosomes line up at the centre of the cell; cell fibres pull the chromosomes apart
3. membranes form around each of the sets of chromosomes, which become the nuclei of the new cells
4. then, the cytoplasm divides


how can plants artificially reproduce?

- a branch is cut off the parent cell
- the stem is planted in damp compost, with hormones often used (to encourage new roots to develop)
- the cuttings are covered in a clear plastic bag to keep it warm and moist
- after a few weeks, new roots develop and then the new plant is produced


explain the process of meiosis

1. before division, DNA is duplicated
2. first division: chromosomes line up in pairs at the centre of the cell
3. pairs are pulled apart by cell fibres; each new cell has only one copy of each chromosome- some of the mother's and father's chromosomes. This mixture of chromosomes gives the offspring variation
4. second division: chromosomes line up again in the centre of the cell, and the arms of the chromosomes get pulled apart
5. this results in four haploid gametes, which only have a single set of chromosomes


what does the word 'reproduction' mean?

the ability of living things to produce new living things of the same species