B1h Flashcards
What are some uses of plant hormones?
- selective weed killers
- growing cuttings from root powder
- controlling the ripening of fruit
- controlling dormancy
How do selective weed killers work?
- most weeds growing in fields of crops or lawns are broad-leaved, grasses and cereals have very narrow leaves
- selective weed killers have been developed from plant hormones that only affect broad-leaved plants
- they disrupt their normal growth patterns, and soon kills them, while leaving grass and crops untouched
How does growing from cuttings with rooting powder work?
- cutting are a part of a plant that has been cut off
- normally planting it does nothing
- but by adding rooting powder, which contains plant hormones, they produce roots rapidly and start to grow as new plants
- enabling growers to produce lots of clones of really good plants very quickly
How does controlling the ripening of fruit work?
- use plant hormones to delay the ripening of fruit while on the plant or during transport
- unripe fruit are firmer and less easily damaged
- ripening hormone added to ripen fruit on the way to the supermarkets
How does controlling dormancy work?
- many seeds won’t germinate (start growing) until they’ve gone through dormancy
- gibberellin is a hormone that breaks this dormancy and allows seeds to germinate
- commercial growers can treat seeds with gibberellin to make them germinate at anytime of year
- it also helps make sure all the seeds in a batch germinate at the same time
What is the ‘genetic’ size order?
- nucleus
- chromosomes
- genes are a short length of a chromosome
- DNA is a short length of a gene
What are the sources of genetic variation?
- gamete formation
- fertilisation
- mutation
How does gamete formation cause genetic variation?
- gametes are made through meiosis
- the body cells splits in half twice to form 4 cells, so these cells have half of the chromosomes of a normal body cell
- the shuffling is random, as your chromosomes are from both of your parents
- this leads to genetic variation
How does fertilisation cause genetic variation?
-fertilisation is random, as you do not know which two gametes are going to join together
How do mutations cause genetic variation?
- mutation is a change in the genetic code
- occasionally a gene can mutate
- this can create new characteristics, increasing variation
What traits can be due to your genes and the environment?
- health
- intelligence (genes probably determine maximum IQ)
- sporting ability (genes probably determine potential)
What are the issues of knowing inherited conditions in your family?
- is it right for someone to risk passing on a genetic condition to their child, is it fair to put them under pressure not to
- is it right to terminate the pregnancy if the foetus is tested for genetic conditions and comes is positive
What is dormancy?
- certain conditions a plant needs to go through
- e.g. a period of cold or dryness
What are alleles?
-different versions of the same gene, e.g. brown and blue eyes
What is a genotype?
-the genetic makeup, i.e. the alleles you have for a particular gene
What is a phenotype?
-the outwardly shown characteristic, e.g. blue eyes
What does heterozygous mean?
-two different alleles
What does homozygous mean?
-two alleles the same
