Module 5: Heredity Flashcards
Asexual reproduction
Requires only one parent-A parent cell replicates and divides generating offspring that are genetically identical.
-Contains the same genetic material as the parent
EG: Bacteria- binary fission
Sexual reproduction
Requires two parents.
-A haploid (n) gamete from each parent combines to produce genetically unique diploid (2n) offspring
-EG: Humans- egg and sperm will meet
Haploid and diploid
Haploid: one copy (n), diploid: two copies (2n)
How do plants sexually reproduce?
-Flowers are key in plant sexual reproduction (they are the reproductive organs of plants)
-The fusion of two haploid gametes
-They produce male sex cells (pollen grains) and female sex cells (ovum- contained in the ovules)
-These two must meet for pollination and for reproduction to begin.
-After pollination occurs, fertilization occurs and the ovules grow into seeds in a fruit which disperse once ripe.
-Stamen (male), pistil (female)
How do plants asexually reproduce?
Bulbs:Underground storage organ that consists of a short stem surrounded by fleshy leaves. New shoots (plants) develop from the bulb. (Example- Onion)
Runners: Side branches that grow close to the ground and develop new plantlets on them.(Example- Strawberries)
Apomixis: Some plants are able to produce offspring from special generative tissues, without involving fertilisation or the production of seeds.This generative tissue gives rise to new plantlets that produce asexual seeds. Plantlets that arise on leaves and their seeds grow into individuals that are
genetically identical to their parents.(Examples-Kangaroo Grass)
How are gametes produced in animals?
-Gametes are produced by each parent organism through meiosis
-Each gamete contains half the necessary number of chromosomes- through ext or int fertilisation
Internal fertilisation (advantages and disadvantages)
Increased likelihood of fertilization as egg and sperm are in close proximity- increased protection from the environment- leading to higher survival rates of offspring.
Fewer offspring are produced, more difficult to bring makes and females into contact- higher risk of sexually transmitted infections etc
Internal fertilisation
Sperm and egg come together within the female body (in mammals it is the result of sexual intercourse)
External fertilisation
Sperm and egg unite outside of the female body (amphibians, fish-usually an aquatic environment)
External fertilisation (disadvantages and advantages)
Results in the production of a large number of offspring, easier to find mates as the gametes released can drift (wind, water etc), ore genetic variation, less competition- due to spread
Simpler behavioural process
Environmental hazards such as predators reduce the chance of surviving into adulthood. Gametes can go unfertilized and wasted.
Not guaranteed that sperm will encounter eggs. Greater chance of desiccation of gametes/zygotes
Asexual reproduction in animals
Budding:Daughter cell develops in the mode of an outgrowth or a bud (pinching off) from the parent cell by mitosis. (Coral)
Fragmentation: Where the body of an organism breaks into two or more types, each of which develops into a new organism due to the presence of stem cells.
Parthenogenesis: Where offspring develop from the gamete without prior fertilization from the male gamete (unlike sexual reproduction
Reproduction in bacteria (asexual binary fission
- The cell elongates- building more cell walls (full adult size)
- The bacterial genome replicates and remains attached to the membrane. At the same time any plasmids (small circular DNA) that are present, replicate.
- Duplicated DNA begins to separate, moving towards the poles as the cell elongates more.
4-5. Cleavage furrow begins to form in cell walls, in cleavage furrow. - Two identical daughter cells are produced.
-Some bacterial species use other patterns of cell division to reproduce- some grow larger than the adult size, undergo multiple divisions and produce many offspring.
Reproduction in fungi
Sexual: Specialized haploid (n) hyphae fuse together to form a diploid cell (2n). This genetically unique diploid cell then undergoes meiosis to produce new haploid (n) spores
Asexual: Fragmentation, budding, spores (Pieces of hyphae can separate and become their own colonies, mitosis produces genetically identical cells to the parent, which are distributed into the environment by wind or vectors etc)
Reproduction in protists
Sexual: Two haploid cells fuse to form a new cell, undergoes meiosis to form new haploid cells, or diploid cell undergoes meiosis to produce 4 gametes that fuse during fertilisation
Asexual: Binary fission (replicates genetic material and then splits), budding (gives rise to small bud that separates), multiple fission (several individuals form out of the parent)
Advantages and disadvantages of sexual reproduction
High genetic diversity
-Less prone to environmental change
-Facilitates adaptation
-Energy costly
-Requires two parents
-Courtship is time and resource-consuming
Advantages and disadvantages of asexual reproduction
-Energy efficient
-Requires 1 parent only
-No courtship is required
-High amount of gametes
Low genetic diversity
-More prone to environmental change
-Inhibits adaptation and evolution
Why do some organisms reproduce both ways?
-Organisms that can produce both sexually and asexually, are able to receive the advantages from both.
-When the number of males is high and the conditions aren’t favourable in a certain area, organisms are more likely to sexually reproduce than asexually reproduce.
Process of fertilisation itself (sperm and egg fusion)
1.Sperm makes contact with the egg and burrows through corona radiata.
2.Sperm attaches to receptor of zona pellucida
3.Digestive enzymes realeased across the acrosome and sperm burrows through zona pellucida.
4.Plasma membranes of sperm and egg fuse.
5.Sperm nucleus enter egg.
Process of implantation
- Fertilisation
2.Zygote
3.Morula 3-4 - Blastocyst 4-7
- Implantation 74
LH
-Helps control the menstrual cycle, triggering the release of an egg from the ovary- helps the development of the egg
-Secreted by the pituitary gland
FSH
Helps control the menstrual cycle and stimulates the growth of eggs in the ovaries.
Progesterone
-Helps prepare the uterus for the implantation of a fertilized egg and maintains pregnancy.
Estrogen
Regulation of the reproductive system.
GnRH
-Triggers the ovaries to make progesterone and estrogen
-Triggers the pituitary gland to secrete LH and FSH
-Produces estrogen and progesterone to regulate ovarian and menstrual cycles.
-Secreted by the hypothalamus
What do oestrogen and progesterone do?
Estrogen and progesterone levels regulate ovarian and menstrual cycles and create ideal conditions for ovulation, implantation and maintaining pregnancy.
What is artificial pollination?
1.Pollem (sperm) removed from the stamen of one plant
2.Pollen applied to the stigma of another plant
3. Pollen fertilizes the ovum.
-Both agricultural and domestic plant breeders use this process to breed plants with specific characteristics such as colour, size and yield.
(VANILLA- one species of bee)
What is artifical insemination?
1.Detection of female cows in oestrus
2.Collection of semen
3. Insemination usually performed using an insemination gun which shoots semen into the cervix of the desired animals.
Selective breeding?
-The intentional mating of individuals with desirable traits in the hope that offspring will express those same traits in their phenotype
-Its prevalent in sheep pigs, cows, chickens, fish, prawns etc
-Sheep have been selected for the quality and quantity of the wool they grow and beef cattle for their muscle mass
1.Determine the desired breed
2.Interbreed parents that show the desired trait
3.Select the offspring with the best form of the trait and breed these offspring
4.Continue this process until the population reliably produces the desired trait
-EXAMPLE: Jersey or Angus cows
Genetic engineering
-Process of a gene being removed from one species and inserted into the genome of another species
-The protein produced by the gene is then expressed in tge genotype of the second species
Genetic engineering plants and animals examples
BT
-Bt is a bacteria species producing a toxic that is toxic to select insect pests
-Gene is isolated from BT and inserted into cotton and rice to produce a transgenic species called BT cotton or rice.
-Natural insecticide that kills insects- higher yield
GM Atlantic salmon
-Growth hormone from the chinook salmon and a gene from the eel-like ocean pout which switches on the Chinook’s growth hormone
-Allows them to grow all year round.
Cloning
Cloning is the process by which genetically identical copies of an organism are made without using the process of sexual reproduction.
The most common method (and the oldest) is grafting. The plant and fruit produced is a clone of the original plant. This is seen commonly in fruit crops.
IDEA- Contributions of scientists
Without knowing Mendel, Chargaff and Watson and Crick we wouldn’t be able to manipulate at all.
Mitosis
-Cell division resulting in two identical daughter cells, with the same number and kind of chromosomes as the parent cell.
-Mitosis plays an important role in growth, repair, asexual reproduction and genetic stability
Interphase of Mitosis
Cell prepares itself for division
-DNA replication occurs to produce two copies of each chromosome.
-Period of growth and normal activity
Prophase
Duplicated chromosomes condense
-Chromosomes become visible and the centrioles separate and move to opposite poles of the cell.
-Microtubules that are apart of mitotic spindles that lengthen and shorten to pull chromatids apart.
Metaphase
Prometaphase: Nuclear envelope breaks down
-Pairs of condensed chromosomes (called sister chromatids) line up along the equator of the cell
-Each pair of chromosomes are attached to different spindle fibers to move in the opposite direction.
Anaphase
Chromatids separate and move towards opposite poles of the cell by the mitotic spindle
There is now only one copy of each chromosome at either end of the cell.
Telophase
Two new nuclear envelopes form around the separated sister chromatids
Chromosomes spread out again
-Nucleolus reappears and spindle fibers disappear
Cytokinesis
Two daughter cells are separated by. The tightening of a ring of proteins around the middle of the dividing parent cell- the two nuclei are squeezed apart
-Cytokinesis occurs simultaneously to anaphase and telophase- the pinching of the cellular membrane begins to happen as chromosomes are separated and new nuclei are formed.
