MOD 5 Flashcards
Reproduction, Cell replication
What is reproduction?
Production of offspring (necessary for continuation of life)
What is asexual reproduction?
New offspring produced by a single parent (does not involve gametes)
What are the disadvantages of asexual reproduction?
Less genetic diversity and vulnerable to genetic changes in environment
What are the advantages of asexual reproduction?
More offspring when environment is favourable and energy efficient
What is sexual reproduction?
Fusion of two gametes (male and female) where genetic information from each parent is passed on in the chromosome
What are the disadvantages of sexual reproduction?
Slow population growth
What are the advantages of sexual reproduction?
Offspring are genetically diverse ensuring continuity of species
What are gametes?
Haploid cells that contain one copy of chromosome and formed by meiosis
What happens when a haploid sperm cell and a haploid egg cell fuse?
They form a fertilised diploid
What is a zygote?
Fertilised egg
What are hermaphrodites?
An organism that has both male and female reproductive organs. (eg. snail)
What are the advantages of hermaphrodites?
Can increase quickly when low population density
What are the disadvantages of hermaphrodites?
Large amounts of energy to grow and maintain two sets of reproductive systems (fewer combinations of genes and less genetic variation)
What is internal fertilisation?
Eggs fertilised inside female’s body
What are the advantages of internal fertilisation?
Higher chance of fertilisation and control of mate choice allowing quicker natural selection
What are the disadvantages of internal fertilisation?
Requires more energy and produces fewer offspring
What is oviparous?
May develop a shell and be laid in the external environment (vulnerable to predation)
What is external fertilisation?
Both sperm and egg released into environment and fertilised outside the body - synchronisation of reproductive cycles
What are the advantages of external fertilisation?
Efficient and often produce large number of offspring with a wide dispersal
What are the disadvantages of external fertilisation?
Lower chance of fertilisation and often limited to aquatic environments
What is an example of external fertilisation?
Coral spawning - signaled by environmental cues (abiotic and biotic)
What are hormones?
Chemical substances that act as messengers in the body and coordinate functions
What is the pituitary gland?
Endocrine gland at the base of the brain and is the master gland that secretes hormones that stimulate or inhibit other endocrine glands
What are sex hormones?
Produced in the ovaries or testes and in pituitary gland and adrenal cortex - different from gametes (sex cells)
What are gonads?
Reproductive organs
What is puberty?
Reproductive organs mature and begin their function
What is the role of oestrogen?
Female hormone controlling development and functioning of reproductive system (particularly menstrual cycle)
What is the role of progestogens?
Version of progesterone and stimulates secretion of milk in mammary glands
What is the role of androgens?
Male hormones eg. testosterone which controls development and function of male sex organs
What is the role of inhibin?
Stops pituitary gland from producing LH & FSH
What are gonadotropin releasing hormones?
Initiates pituitary gland to produce sperm
What is FSH?
Follicle stimulating hormone to trigger growth of eggs in ovaries
What is LH?
Luteinising hormone to trigger ovulation
What happens in the follicular phase?
Follicle in the ovary grows and matures (menstruation also occurs during this phase - beginning of follicular)
What happens in the luteal phase?
After ovulation where the corpus luteum (build up lutein) forms and produces progesterone
What is fertilisation?
Fusion of two gametes to form a diploid zygote
Where does fertilisation take place?
Fallopian tubes
How many layers does the sperm need to go through to reach the egg?
5
What is a blastocyst?
Ball of rapidly dividing undifferentiated cells
What is trophoblast?
Outer cells of blastocyst to provide nutrients to embryo
When and what happens during implantation?
6-10 days after ovulation to implant into endometrium (prepped by progesterone and oestrogen)
What is the role of oestrogen during ovulation?
Promotes growth of endometrium of the uterus
What is progesterone?
Stimulates secretion of mucus by cells lining the endometrium and preps uterus for pregnancy
What is hCG?
Human chorionic gonadotropin - stimulates corpus luteum to produce progesterone to maintain pregnancy
What is the role of relaxin?
Prepare body for childbirth and increase elasticity of ligaments and expansion of pelvis
What is the role of oxytocin?
Causes uterine muscles to contract and cervix to relax - begin positive feedback loop
What is the positive feedback loop?
Repeated stimulus where contractions cause secretion of oxytocin and prostaglandin causing contractions
What is the role of endorphins?
Reduce pains and suppresses immune system
What is the role of adrenaline?
Stimulates contractions
What is pollination?
Transfer pollen from anthers to the stigma through pollinators
What is self-pollination?
Pollen fertilises ova of the same plant
What is cross-pollination?
Pollen fertilises ova of a different plant of the same species
Why is self-pollination better than cross-pollination?
Requires less energy and no reliance on biotic or abiotic factors
Why is cross-pollination better than self-pollination?
Genetic variation in offspring
What is sexual reproduction in plants?
Seeds disperse over a wide distance to increase continuity of species in other locations
What is asexual reproduction in plants?
Cloning an adult plant with identical genetic material
What are runners?
Stems growing horizontally above ground eg. strawberries
What are rhizomes?
Horizontal underground stems eg. bamboo
What are tubers?
Attached to the roots and bud on the roots eg. potatoes
What are bulbs?
Stem attached with short underground stem eg. onion
What are suckers?
Roots of some plants produce suckers which rises into a new plant
What are the steps for flower fertilisation?
- Male gametes (pollen) carried from anther to stigma (female part) ⇒ gamete transfer (pollination)
- Pollen composed of: Tube cell & Generative cell
- Pollen deposited at stigma - pollen tube cell creates pollen tube from stigma down the style towards ovary
- Generative cell travels down this tube and divides to form two sperm cells
- Two sperm cells enter one of the ovules (contain two polar nuclei and an egg) within the plant’s ovary
- After ovulation ⇒ ovule matures into a seed (contains fertilised egg and endosperm) - may then be dispersed to germinate
- Zygote develops into embryo ⇒ into new plant by mitosis after germination
- After fertilisation petals die off & ovary grows into fruit to nourish and protect seeds & encourage dispersal when mature
What are hyphae?
Tiny branching filaments on multicellular fungi
What is mycelium?
Main body of the fungus
What are spores?
Tiny unicellular reproductive cells (form on special hyphae) that are produced in great numbers
Where are spores produced?
Sporangia
What is asexual reproduction with spores in fungi?
Special hyphae produce spores by mitosis and are released
What is sexual reproduction with spores in fungi?
Two hyphae from different mycelia fuse to create a diploid zygote (genetic material from both parents)
What is fragmentation in fungi?
Multicellular fungus dividing into fragments (separate organisms with identical gametes)
What is budding in fungi?
Asexual reproduction where a new individual grows from a bud on the parent
What are the steps of budding in fungi?
- Formation of bud on the side of the parent cell followed by nuclear division to provide each cell with a genetically identical nucleus (bud is initially smaller than parent cell but grows in size as it matures)
- After bud is nearly as large as parent, cytokinesis occurs (separation of cytoplasm to form two separate cells)
What is cytokinesis?
Separation of the cytoplasm into two separate cells or division
What type of cell are bacteria?
Prokaryotes
What is the shape of bacteria DNA?
Singular circular chromosomes
What is bacterial reproduction by binary fission?
Main method of asexual reproduction where a single bacterial cell divides into two identical daughter cells
What is the origin of replication?
Section where duplication of the chromosome first occurs (starting point for chromosome)
What type of daughter cells are formed after binary fission in bacterial reproduction?
One copy of chromosomes will end up in the genetically identical daughter cells - to the parent
What type of organisms are protists?
Eukaryotic mostly unicellular organisms
What is asexual reproduction in protists (binary fission)?
Single-celled organism divides into two identical daughter cells (similar to bacterial fission) - involves mitosis and formation of spindle in the cytoplasm to distribute chromosomes equally
What is multiple fission in protists?
When the nucleus divides repeatedly to produce a number of daughter nuclei which eventually become daughter cells
What is asexual reproduction in protists (budding)?
Daughter cells (exact copies) gradually grow from parent cell and eventually detach when mature (bud out)
What is sexual reproduction in haploid protists?
Two haploid protists fuse to form a diploid zygote where the zygote undergoes meiosis to form new haploid cells
What is sexual reproduction in diploid protists?
Adult diploid cell undergoes meiosis to produce haploid cells (gametes) ⇒ fertilisation of different haploid cells forms a diploid zygote developing into adult diploid cell
What is DNA?
Deoxyribonucleic acid (devoid of one oxygen) and contains our genetic material
What is genetic material?
(Chemical) carries code for all observable inherited traits ⇒ in strands chromosomes (organised bundle of DNA coiled around protein, histone) that exist in the nucleus of cells
What is a nucleotide?
Phosphate group joined to a deoxyribose sugar which is attached to a nitrogenous base of adenine, thymine, cytosine or guanine
What is a nitrogenous base?
Nitrogen-containing molecular units that make up a nucleic acid
What is the structure of DNA?
Double Helix shape (twisted ladder): two sides ‘backbone’ made up of alternating sugar and phosphate units
What are the rungs of the DNA ladder?
Pairs of nitrogenous bases (AT double bond, GC triple bond) joined with hydrogen bonds (easily broken)
How are the strands of DNA built?
Antiparallel ladders that run in opposite directions (5’ prime ⇒ 3’ prime and 3’ prime ⇒ 5’ prime)
What is the Watson-Crick DNA model?
Two strands/chains of nucleotide pairs that encode genetic information of the DNA double helix are held together by hydrogen bonds between nitrogenous bases on opposite strands
How is DNA structured in eukaryotic cells?
DNA molecules wound into tightly coiled structures = chromosomes, they wind around histones (proteins)
How can a human karyotype be used?
To compare chromosomes (identify disorders) since every single cell in an organism contains a complete set of organism’s DNA
What DNA is found in prokaryotes?
Circular chromosomes which float in nucleoid (dense region of cytoplasm) - may also contain plasmids
What DNA is found in eukaryotes?
Contain membrane bound organelles including nucleus (where majority of DNA is located) - DNA exists in many separate linear chromosomes
What DNA is found in eukaryotes?
Eukaryotes contain membrane-bound organelles, including a nucleus where the majority of DNA is located. DNA exists in many separate linear chromosomes, which are larger and more complex than prokaryotic DNA. Some DNA is also found in mitochondria (mtDNA) and chloroplasts, controlling processes in these organelles.
What is interphase?
Interphase is the growth phase of the cell cycle, broken down into three stages: G1 (growth), S (DNA synthesis/replication), and G2 (growth & preparation for mitosis). It constitutes about 90% of the cell cycle, during which the cell grows by producing proteins and additional copies of organelles.
What is the purpose of DNA replication?
DNA replication creates copies of DNA so that new cells can be produced, occurring in the nucleus.
What is helicase?
Helicase starts from a point origin and unzips the two strands by breaking the hydrogen bonds, creating a replication fork.
What is primase?
Primase is made of RNA and acts as the initializer for polymerase by attaching primers, which are short fragments of DNA that serve as starting points for polymerase.
What is DNA polymerase?
DNA polymerase replicates the DNA to build new strands in the 5’ to 3’ direction (leading strand), while the other is the lagging strand requiring many primers. It also has proofreading mechanisms to prevent incorrect DNA replication.
What are Okazaki fragments?
Okazaki fragments are uneven strands produced by DNA polymerase due to the lagging strand.
What is ligase?
Ligase is the enzyme that glues and seals Okazaki fragments.
What happens in the synthesis stage?
During the S phase, chromosomes replicate, and two chromosome copies or chromatids are held together by a centromere.
What is the semiconservative model?
The semiconservative model describes how two parental strands separate and each makes a copy of itself, resulting in one original strand and one new strand.
What is the conservative model?
The conservative model refers to the creation of an entirely new double-stranded molecule while conserving the original parent strand.
What is the dispersive model?
The dispersive model describes how parental strands are distributed randomly.
Why is DNA replication essential for continuity of species?
DNA replication is essential for cell replication (meiosis and mitosis), supporting growth, repair, and reproduction. It allows large amounts of genetic information to be passed from cell to cell or generation to generation.
How does DNA replication maintain genetic stability?
DNA replication produces nearly identical strands of DNA, enabling favorable traits essential for survival to be passed onto new cells, ensuring proper functioning in somatic cells and favorable traits in gametes.
How does DNA replication introduce genetic variation?
Low levels of mutations (errors from polymerase) are introduced during DNA replication, allowing for low levels of variation, which enables natural selection and increases the likelihood of species survival in changing environments.
