3. Repriduction And Inheritance Flashcards
1
Q
Does SEXUAL reproduction produce genetically identical or genetically varied offspring!?
A
. This produces genetically varied offspring using specialised cells called gametes.
2
Q
Does ASEXUAL reproduction produce genetically varied or genetically identical offspring
A
. This produces genetically identical offspring. Gametes are not needed and there is only one parent involved
3
Q
What advantages does SEXUAL reproduction pose !?
A
. This method is an advantage in a changing environment or when there is a threat of disease from pathogens
4
Q
What advantages does ASEXUAL reproduction pose!?
A
. The offspring, called CLONES, are at an advantage in a stable environment because it allows parent plants with advantageous adaptations to produce offspring with the same beneficial characteristics
5
Q
In order to FERTILISE a plant the male (pollen) and female (ovum) gametes must…
A
. … fuse, to form a single cell called a ZYGOTE
6
Q
How does a ZYGOTE transform into an embryo !?
A
. The zygote will divide many times by MITOSIS to form all the cells of the new organism
7
Q
Where is the STAMEN of the INSECT pollinated flower located!?
A
. Enclosed within the flower
8
Q
Where is the STAMEN in a WIND pollinated plant located !?
A
. Exposed, outside of petals
9
Q
The STIGMA of an INSECT pollinated flower is…
A
. … Enclosed within the flower and sticky
10
Q
The STIGMA of a WIND pollinated flower is…
A
. … Exposed outside of petals, often, “feathery”.
11
Q
What features to the PETALS of INSECT pollinated flowers obtain !?
A
. They are large and brightly coloured
12
Q
What features do the PETALS of INSECT pollinated obtain!?
A
. Small, usually green
13
Q
Do INSECT pollinated flowers have a NECTARY!?
A
. Present- produce sugary fluid to attract insects
14
Q
Do WIND pollinated flowers have a NECTARY!?
A
. Absent
15
Q
POLLINATION: (Gap fill)
1. In plants pollen grains are deposited onto the ______!?
A
. In plants pollen grains are deposited onto the STIGMA
16
Q
POLLINATION:(gap fill)
2. The pollen grain normally grows a ______ ____ which grows down through the _____
A
. The pollen grain normally grows a POLLEN TUBE which grows down through the STYLE
17
Q
POLLINATION: (Gap fill)
3. _______ are secreted at the tip of the tube which digest the tissues of the style
A
. ENZYMES are secreted at the tip of the tube which digest the tissues of the style
18
Q
POLLINATION: (gap fill)
4. When the tube reaches an ovule the male gamete travels through the tube entering the _____ through a small hole called the _________
A
. When the tube reaches an ovule the male gamete travels through the tube entering the OVULE through a small hole called the MICROPYLE
19
Q
POLLINATION:(gap fill)
5. It the fuses with the female gamete (____) in the process of _____________
A
. It the fuses with the female gamete (OVUM) in the process of FERTILISATION
20
Q
POLLINATION:(gap fill)
6. The fertilised ovum divides by _______ to form the embryo
A
. The fertilised ovum divides by MITOSIS to form the embryo
21
Q
POLLINATION:(gap fill)
7. The ovule develops into the ____
A
. The ovule develops into the SEED
22
Q
POLLINATION:(gap fill)
8. The ovary develops into the _____
A
. The ovary develops into the FRUIT
23
Q
What does the ZYGOTE become once the plant is fertilised !?
A
. The zygote develops into an embryonic plant with a small root (RADICLE) and shoot (PLUMULE)
24
Q
What does the OVULE WALL become once the plant is fertilised !?
A
. The ovule wall becomes the TESTA ( hard coating of the seed )
25
Practical: Investigating the conditions needed for seed germination
Cress seeds are added to cotton wool in test tubes.
- Tube A is put in a fridge (no warmth), the rest are kept on the windowsill
- Tube C, the cotton wool is moistened with boiled water and an oxygen absorber (sodium pyrogallol) is added (no oxygen)
- Tube E is wrapped in foil (no light)
- Tube B, the cotton wool is kept dry (no water)
- Tube D has all the conditions present
Check germination after 2-3 days, perhaps combine class results
26
During the Practical (investigating the conditions needed for germination) which seeds germinate !?
. Tube D, all conditions present
. Tube E, no light
27
How do germinating seeds obtain a great deal of energy quickly !?
. They use their food stores, using ENZYMES that break down carbohydrate stores
. These are then used as fuel in respiration to release energy
28
When does a seed stop using their food stores to obtain energy !?
. They used their food stores until the leaves are in a position to Photosynthesise
29
In order to germinate plants need three things:
. Oxygen
. Warmth
. Water
30
Why does a seed need OXYGEN to germinate ?!
. To aerobically respire
31
Why does a seed need WARMTH to germinate!?
. Optimum temperature for enzymes
32
Why does a seed need WATER to germinate !?
. To activate the enzymes
33
What is the FOOD STORE called in young, germinating, plants!?
. Cotyledons
34
A plant can reproduce ASEXUALLY by RUNNERS, how do they work !?
. A new plant is produced where the runner touches the ground
35
A plant can reproduce ASEXUALLY by TUBERS, how do they work !?
. One plant can produce many tubers which can each grow many shoots which form new plants
36
What is a TUBER !?
. Swollen underground stems containing lots of stored food
37
A plant can reproduce ASEXUALLY by BULBS, how do they work!?
. A main shoot will grow out of the parent bulb and another will grow out of the side “daughter” bulb, forming two plants
38
What is a BULB!?
. Underground buds with thick fleshy leaves containing stored food
39
What is An ARTIFICIAL method to grow plants ASEXUALLY!?
. Cuttings
- A piece of a plants stem , with a few leaves attached, is cut from a healthy plant. This is planted in damp compost, where it will grow roots and develop into a new plant
40
What is a NATURAL method of growing a plant ASEXUALLY !?
. Runners
. Tubers
. Bulbs
41
Are gametes diploids or haploids!?
. Gametes are haploids (23 chromosomes)
42
Definition of FERTILISATION:
. Fertilisation is the FUSION of haploid male and female gametes, restoring the diploid number of chromosomes in the zygote
43
Are all sperm cells and all egg cells genetically identical!?
. No, each sperm cell and each egg cell is genetically different due to the process that has created them
44
What is an AMNION !?
. An amnion encloses the developing embryo. The amnion secretes a fluid called AMNIOTIC FLUID
45
What is the function of AMNIOTIC FLUID!?
. It protects the developing embryo against jolts and bumps (mechanical shocks), drying out, and temp. Fluctuations
46
What does the embryo become when it looks human !?
. a FOETUS
47
What are the adaptions of SPERM cells!?
. A tail- called a flagellum- allowing it to swim through the female reproductive system
. A HAPLOID nucleus- has half the number of normal chromosomes
. Many MITOCHONDRIA- to produce energy
. Enzymes in the head- to penetrate egg
48
What is the role of OESTROGEN in the menstrual cycle !?
. Inhibits FSH production (stops another ovum from being matured)
49
Where is OESTROGEN secreted from !?
. (A follicle In the) Ovary
50
What is the target organ for OESTROGEN!?
. Pituitary gland
51
What is the role of PROGESTERONE in the menstrual cycle !?
. FSH and LH inhibited
. Maintains the thickness of the uterus lining
52
Where is PROGESTERONE secreted from !?
. Ovary
53
What organ does PROGESTERONE target !?
. Pituitary gland
. Uterus lining
54
What is the role of FSH in the menstrual cycle !?
. Follicle develops and ovum matures
. Maturing follicles release Oestrogen
55
Where is FSH secreted from !?
. Pituitary gland
56
What organ does FSH target !?
. Follicle In ovary
57
What is the role of LH in the menstrual cycle!?
. Ovulation- follicle In ovary releases mature ovum into the oviduct
. Reminding of follicle (on ovary) becomes corpus luteum
58
Where is LH secreted from!?
. Pituitary gland
59
What organ does LH target !?
. Follicle in ovary
60
What is the role of the PLACENTA!?
. Connected by an umbilical chord, it develops from the embryo. The placenta anchors the embryo in the uterus
. It allows nutrients to move from the mother to the embryo
. It allows metabolic wastes to move from embryo to mother
61
What nutrients does the placenta allows to be transferred from the mother to the embryo !? (Via diffusion)
. glucose, amino acids, salts and oxygen
62
What metabolic waste does the placenta allows to be transferred from the embryo to the mother !? (Via diffusion)
. Carbon dioxide and urea
63
Secondary characteristics in GIRLS are controlled by what hormone !?
. Oestrogen
64
Secondary characteristics in BOYS are controlled by what hormone!?
. Testosterone
65
Secondary sexual characteristics in GIRLS:
. Voice deepens
. Menstrual cycle begins
. Pelvis broadens, preparing for labour + pregnancy
. Armpit and pubic hair growth
. Muscle development and fat deposits on breasts, hips and thighs
. Growth and development of genitalia
. Mood swings and acne
66
Secondary sexual characteristics in BOYS:
. Voice breaks
. Sperm production begins
. Shoulder broaden
. Facial, armpit, body and pubic hair growth
. Greater muscle development
. Growth and development of genitalia
. Mood swings and acne
67
What is MITOSIS!?
. Mitosis is a type of cell division in which a diploid body cell copies itself and finally divides into two identical diploid DAUGHTER CELLS.
68
What are DAUGHTER CELLS !?
. Daughter cells are clones of each other. Every base pair of their DNA is identical
69
What is the first step of MEIOSIS !?
1. The parent cell grows
70
MEIOSIS: (gap fill)
2. The ___ __________ (is copied) to form two copies of each chromosome. These copies (__________) are joined together at a single point (the centromere)
. The DNA REPLICATES (is copied) to form two copies of each chromosome. These copies (CHROMATIDS) are joined together at a single point (the centromere)
71
MEIOSIS: (gap fill)
3. The nuclear membrane breaks down. The _________ _____ __ ___________ ____ ________
. The nuclear membrane breaks down. The HOMOLOGOUS PAIRS OF CHROMOSOMES JOIN TOGETHER
72
MEIOSIS: (gap fill)
4. The homologous pairs of chromosomes ________ ________ __ ___. Then attach to the spindle fibers in _____, at the centre of the cell
. The homologous pairs of chromosomes EXCHANGE SECTIONS OF DNA. Then attach to the spindle fibers in PAIRS, at the centre of the cell
73
MEIOSIS: (gap fill)
5. The _________ _____ __ ___________ are ______ _____ and move to opposite ends of the cell. The cell divides
. The HOMOLOGOUS PAIRS OF CHROMOSOMES are PULLED APART and move to opposite ends of the cell. The cell divides.
74
MEIOSIS: (gap fill)
6. The chromosomes line up along the ______ of the cell, attached to the spindle fibers. The __________ ________ and move to _______ ends of the cell. Each cell divides again
. The chromosomes line up along the CENTRE of the cell, attached to the spindle fibers. The CHROMATIDS SEPARATE and move to OPPOSITE ends of the cell. Each cell divides again
75
How many cells does MITOSIS produce!?
. MITOSIS Produces two genetically identical daughter cells
76
How many cells does MEIOSIS produce!?
. MEIOSIS produces four genetically NON- identical daughter cells
77
How many cell divisions occur in MITOSIS!?
. Mitosis involves one division
78
How many cell divisions occur in MEIOSIS!?
. Meiosis involves two cell divisions
79
Does MITOSIS produce Haploid or diploid cells in humans!?
. Mitosis produces diploid cells in humans
80
Does MEIOSIS produce haploid or diploid cells in humans !?
. Meiosis produces haploid cells in humans
81
Where does MITOSIS occur in the human body !?
. Mitosis occurs throughout the human body
82
When does MITOSIS occur !?
. During:
- growth and repair
- cloning
- asexual reproduction
83
What is MEIOSIS!?
. Meiosis is the type of cell division which gives rise to cells that are genetically DIFFERENT
84
Where does MEIOSIS occur in the human body!?
. Meiosis takes place in the SEX ORGANS
85
When does MEIOSIS occur!?
. During:
- only used to produce gametes
- sexual reproduction
86
Why, Due to MEIOSIS, is offspring genetically different from each other and their parents!?
. Meiosis produces four genetically different haploid cells. As a result of MEIOSIS and FERTILISATION, the maternal and paternal chromosomes meet in different combinations in the zygotes
87
What is the first stage of MITOSIS!?
. The cell grows
88
MITOSIS: (gap fill)
2. The ___ __________ (is copied) to form two copies of each chromosome. These copies (_________) are joined together at a single point (the centromere
. The DNA REPLICATES (is copied) to form two copies of each chromosome. These copies (CHROMATIDS) are joined together at a single point (the centromere
89
MITOSIS: (gap fill)
3. The nuclear membrane breaks down. The ___________ ____ __across the centre of the cell, attached to special _______ fibres
. The nuclear membrane breaks down. The CHROMOSOMES LINE UP across the centre of the cell, attached to special SPINDLE fibres
90
MITOSIS: (gap fill)
4. The __________ (copies of chromosomes) are ______ _____ and move to opposite ends of the cell
. The CHROMATIDS (copies of chromosomes) are PULLED APART and move to opposite ends of the cell
91
MITOSIS: (gap fill)
5. The ________ and ____ ________ _______ to form two identical cells
. The CYTOPLASM AND CELL MEMBRANE DIVIDES to form two identical cells
92
How may chromosomes in a DIPLOID!?
. 46
93
How many chromosomes in a HAPLOID !?
. 23
94
Insect or wind pollinated !?
Insect pollinated
95
Insect or wind pollinated !?
Wind pollinated
96
What is the **genome** !?
The Genome is the entire DNA of an organism
97
What is a **gene** !?
A gene is a section of a molecule of DNA that codes for a specific protein
98
Where are **genes** located !?
The **nucleus** of a cell contains **chromosomes** on which genes are located
99
On what does a **gene** provide genetic information!?
It provides information on the sequence of amino acids in a protein (e.g. an enzyme)
100
What do the **proteins** *coded for by a **gene*** control !?
These proteins, then control, chemical reactions, growth, coloration, or inheritable characteristics
(E.g. the height of a pea plant, or the colour of eyes)
101
Is the code produced by **genes** **selective** or **universal** !?
The code is a universal. Bacteria, read it in the same way that animals and plant cells read it.
102
Within **DNA** what codes for a **specific amino acid** !?
In DNA, the sequence of three bases, codes for a specific amino acids
(*E.g. the sequence TAG. Would code for one amino acid whereas CCG would code for a different amino acid in the chain of amino acids, making up the protein.*)
103
What is a **codon**!?
We refer to every three bases as a **codon**
E.g. TAG or CCG
104
Why is DNA wrapped into **chromosomes**!?
Because the DNA is enormously long, it is wrapped up in structures called chromosomes
105
How many **chromosomes** does each person have !?
Each person has **two** of each chromosome.
(One of each pair comes from the father, the other from the mother.)
106
Why are *chromosomes* **homologous** !?
**Genes**, controlling specific characteristics are situated at the **same** point on each Chromosome, (*so we say the chromosomes are homologous*)
107
What is a **genome**!?
A **genome** is the entire genetic information of an organism
(*the amount present in a diploid cell*)
108
Name the bases:
Adenine
Thymine
Guanine
Cytosine
109
Describe the **structure of DNA** :
. Double stranded
. Coiled into helix
. Sugar phosphate backbone
. Polymer made up of nucleotides
. Complementary base pairing
110
Which animal cell **doesn’t** contain a **nucleus** !?
Red blood cell
111
What is the role of the **nucleus** !?
The role of the nucleus is to control the activities of the cell, using the genes
112
Where is **genetic information stored** *within the nucleus* !?
The nucleus contains the genetic information needed to produce a new cell. **This information is stored on chromosomes**
113
Label:
114
How many **autosomes** are there in **humans** !?
In humans of the 23 pairs of chromosomes, **22 pairs are called autosomes**
115
What is the 23 pair of **chromosome** in humans !?
The 23rd pair are the sex chromosomes, and these determine the sex of the individual
116
How many **matching** pairs of chromosomes do **males** have !?
The cell from the male has **22 chromosomes that pair up** and two that do not form a matching pair X and Y chromosomes
117
How many **matching** pairs of chromosomes do **females** have !?
A body cell from the female has **23 matching pairs**, including X chromosomes
118
What are pairs of **matching chromosomes** Called !?
Pairs of matching chromosomes are called **homologous pairs**
119
What do **homologous pairs of chromosomes** consist of !?
Homologous pairs carry genes for the same features, and these genes are arranged in the same position and sequence along the chromosome
120
What is the **locus** !?
The position of the gene within a chromosome
121
What are **histones**!?
Histones are **structural proteins** that hold the long molecule of DNA within a chromosome in place
122
By what process does **DNA** replicate itself !?
DNA can replicate itself during **mitosis**
(*every cell except egg and sperm cells*)
Each new cell or receive exactly the same type and amount of DNA- they are **genetically identical**
123
What is the role of the **gene** !?
Genes instruct cells to produce a particular protein, which then leads to the development of features
124
What is the definition of an **allele**!?
Different versions of genes
125
An example of when chromosomes carry **genes for the same features**, but in a different **Locus**:
The version of a gene on one chromosome may code for brown eyes. Whereas the version of the gene on the other chromosome a code for blue eyes
126
How do **alleles** arise !?
Alleles arise because of **mutations**
127
Are both features expressed if you have **two different alleles**!?
Not both features are expressed if you have two different alleles e.g. brown hair, blonde hair. This is because one of the alleles is **dominant** and one is **recessive**.
128
Definition of a **dominant allele**:
A dominant allele only needs one allele present to be expressed and **will show its effect**
129
Definition of a **recessive allele**:
A recessive allele needs two alleles present to be expressed, and **will only show up in the appearance of the person if there is no dominant allele present**
130
Definition of a **codominant allele**:
A co-dominant allele will affect the phenotype equally in the presence of another co-dominant allele (*both of alleles have capital letters*)
131
Who worked out the chemical structure of **DNA** in 1953!?
James Watson and Francis crick
132
What did James Watson and Francis crick work out about the chemical structure of the DNA?
. DNA consists of **two polynucleotide strands**.
. The two strand coil round each other in a **double helix.**
. The **backbone is a sugar-phosphate** arrangement
. The bases project was the inside of the double helix.
. DNA is wrapped around a **histone.**
133
What is the name of the **two strands of molecules** that make up **DNA** !?
Nucleotides
134
What does each **nucleotide** contain !?
Each nucleotide contains a **sugar molecule (deoxyribose)** a **phosphate group**, and a **nitrogenous base** containing group called a base
135
When the four bases complimentary base pair, what is the bond between them made from?
They are called hydrogen bonds
136
What do **nucleotides** form when they join together !?
Individual nucleotides join together to form a **polynucleotide**, bonds form between **sugar** and the **phosphate** molecules
137
What is the bond between the **sugar** and the **phosphate** molecules called that joins two **nucleotides** together to form a **polynucleotide**!?
A **Phosphodiester bond**
138
Question: there are 240 bases, 70 are thymine, calculate the number of each other base.
T = 70
A = 70
G = 50
C = 50
139
What are the **environmental factors** that can affect the characteristics of species?
Climate,
diet,
culture,
lifestyle,
and accidents during lifetime
140
What do **environmental factors** that can affect the characteristics of species mean?
In this instance, ‘environmental’ sympathy means outside of the organism
141
Why do **continuous features** often vary !?
Continuous features often vary because of a combination of genetic and environmental causes
142
Definition of a **cell**:
The basic structural unit of living organisms
143
Definition of a **nucleus**:
Cell organelle that contains chromosomes or genetic information that controls the activities of the cell
144
Definition of a **chromosome**:
. Made of DNA
. genes located on
. found in the nucleus
145
Definition of a **gene**:
Section of molecule of DNA coding for a specific protein
146
Definition of a **genome**:
The entire DNA of an organism (*present in a diploid cell*)
147
Definition of a **diploid**:
Number of chromosomes found in body cells, both chromosomes of homologous pair
148
Definition of a **haploid**:
Number of chromosomes found in gametes
149
Definition of an **allele**:
Different forms of the same gene
150
Definition of a **dominant**:
Allele of gene that is expressed
151
Definition of a **recessive**:
Allele that is not expressed in phenotype, when dominant allele is present
152
Definition of a **co-dominant**:
Pattern of inheritance were neither allele of the gene is dominant over the other type, so both alleles are expressed in the phenotype
153
When does **mitosis** occur !?
Mitosis occurs during growth, repair, cloning, and asexual reproduction
- identical
(*my toe GROWS*)
154
What is the definition of **variation**!?
Variation is defined as differences between individuals of the same species
155
What are the *three causes* of **variation** in humans !?
. Genetic
. Environmental
. Combination of both
156
What is a **phenotype**!?
Phenotype is a particular version of a characteristic seen in an individual
157
What is **phenotypic variation** !?
Phenotypic variation is variability in the phenotype that exists in a population as a result of your genetic variation and environmental factors
158
What is **genetic variation** caused by!?
Genetic variation is controlled entirely by genes
159
What is **environmental variation** caused by!?
Environmental variation is caused entirely by the environment in which the organism lives
160
What process produced the **genetic variation** between the **gametes**!?
**Meiosis** creates genetic variation between the gametes produced by an individual
(*this means each gamete carries substantially different **alleles***)
161
During **fertilisation** what does the **fusion** of the male and female gamete form !?
During fertilisation, any male gamete, can fuse with any female gamete to form a **zygote**
162
What did the **random fusion** of gametes at **fertilisation** create !?
This random fusion of gametes at fertilisation creates **genetic variation** between zygote, as each will have a unique combination of **alleles**
163
Examples of **genetic variation** in humans:
. Blood group
. Eye colour
. Gender
164
Examples of **continuous variation**:
(*combination of environmental and genetic causes*)
Tall parents will pass **genes** to their children for height.
The children have the **genetic potential** to also be tall.
However, if their **diet is poor** they won’t grow very well
therefore the **environment** also has an impact on their height.
165
Relationship between **genetic** and **environmental** causes:
Although the **genes** decide what characteristics we **inherit**, the **surrounding environment** will affect how these **inherited characteristics develop**
166
What is **continuous variation** !?
Continuous variation is when there are very many small degrees of difference for a particular characteristic between the individuals,
(*and they are arranged in order and can be usually measured on a scale*)
167
Examples of **continuous variation** :
Height
mass
finger length
168
What causes **continuous variation** !?
Continuous variation is due to the **combined effects** of both **environmental** and **inherited** factors
169
How do we display **continuous variation** on a graph!?
We display this data using a **bar chart** with a **line of best fit**. This usually gives a smooth bell curve because of the small degrees of difference
170
What is **discontinuous variation** !?
Discontinuous variation is when there are distinct differences for a characteristic
171
Examples of **discontinuous variation**:
Blood group
Eye colour
gender
roll their tongue
(*there are no in-betweens*)
172
How do we display **discontinuous variation** on a graph!?
We display this data using a bar chart. This usually gives a step like shape.
173
What is **polygenic inheritance**?
Polygenic inheritance are **characteristics that are controlled by more than one gene, *which influence each other*.**
174
Most phenotypic features, a result of _________ ___________rather than _____ _____ (fill)
Most phenotypic features are a result of **polygenic inheritance**, rather than **single genes**
175
What is are **homozygous chromosomes** !?
If the alleles for a characteristic in a homologous pair are the **same**, the organism is **homozygous** for that characteristic
176
What is are **heterozygous chromosomes** !?
If the alleles for a characteristic of a homologous pair are **different**, the organism is **heterozygous**
177
For **heterozygous alleles** how do we know which **characteristic** will be expressed !?
The characteristic expressed by heterozygous alleles, will depend on which allele is **dominant** and which allele is **recessive**
178
What does the **phenotype** for a particular characteristic depend on !?
The phenotype for a particular characteristic depends on which allele is dominant, and which recessive
179
Definition of **genotype**:
Alleles that an organism possesses for a certain characteristic
E.g. BB (homozygous dominant)
bb (homozygous recessive)
180
Definition of **phenotype**:
**Physical appearance** of an organism *resulting from the* **genotype**
181
What are **monohybrid crosses** !?
Monohybrid crosses are crosses with only one different trait
182
Definition of an **allele**:
Different forms of the same gene
183
Monohybrid genetic crosses:
Phenotype of parents
Genotype of parents
Gametes
Genotype F1
Phenotype F1
Gametes F1 organism
Genotype F2
Phenotype F2
184
What does **F1** stand for !?
Offspring formed by parent
185
What does **F2** stand for !?
Offspring formed when we cross F1 generation
186
Question: cross a**dominant, homozygous** Browne eyed mother, with a **recessive, homozygous** blue eyed father:
187
How many **pairs of chromosomes** do **humans** have?
Humans have **23 pairs of chromosomes**
188
Which **pair of chromosomes** determines the **gender** of the human being !?
The 23rd pair of chromosomes determines the gender of the human being
189
What is always a **female’s** 23rd pair of chromosome !?
Females will always have **XX** as their pair of 23rd chromosomes
190
What is always a **male’s** 23rd pair of chromosome !?
Males will always have **XY** is there a pair of 23rd chromosomes
191
What is the likelihood of having a boy or a girl?
**The likelihood of having a boy or a girl is 50-50**, and is proved with the below genetic diagrams
192
Examples of **polygenic inheritance**:
Human skin colour.
Height
Body mass
193
Why are there so many different **human skin colours**?
Because the amount of melanin in the skin is controlled by **several genes**. Each gene has alleles that promote melanin production and alleles, which do not this produces a **wide range of phenotypes.**
194
What happens **before** a cell divides !?
Before a cell divides, the chromosomes replicate making an exact copy of themselves. This doubles amount of DNA in the cell.
195
Describe the products of **mitosis**:
Mitosis produces genetically identical daughter cells. The cells are diploid. They have one pair of each chromosome in each nucleus.
196
What is **mitosis** used for !?
Mitosis is used for **growth,repair** and **asexual reproduction**
197
Describe the products of **meiosis**:
Meiosis produces haploid gametes (**sperm, eggs, pollen**), which are not genetically identical
198
What is **meiosis** used for !?
Meiosis is only used to produce gametes for **sexual reproduction**
199
What is a consequence of **meiosis** !?
(*genetic variation*)
A consequence of meiosis is that every gamete produced is genetically different
200
Why is every **gamete** produced by **meiosis** *genetically different* !?
This is because it contains different combinations of chromosomes from that persons, mother and father
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What are the **two** ways **variation** in **offspring** occurs !?
. Genetic variation in gametes produced by meiosis
. Random fertilisation of ova by male gametes
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What do we often determine from **family trees** !?
Afton family trees can be used to determine the probability of inheriting a genetic disease
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Definition of a **pedigree diagram**:
A pedigree diagram is a family history for an inherited genetic condition
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How could we work out if the disease was dominant or recessive !?
Use F, C and H is the example the parents are not affected, but had an infected daughter. The daughter must have inherited one allele from each parent.
If the disease was dominant and the parents had just one copy of the faulty allele, they would be affected however another parent is but they still had an infected daughter. Therefore the disease is **recessive**
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How can we tell the **genotype** of F and C !?
We can also tell the **genotype** of F and C. This is because the parents must be **heterozygous** and contain one normal allele and one faulty allele. They must’ve passed on a faulty allele to their daughter, but do not exhibit the disease so much have one normal allele
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Definition of a **mutation**
A mutation is a change in the sequence of bases in DNA
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What are the **three** different types of **mutation**!?
Replacement of a single base pair with a different pair
In addition or deletion of one or more base pairs
Chromosomal mutation
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What is the result of **replacement** or an **addition** or **deletion** **mutation**!?
It gives a change in the DNA sequence, which intern changes the sequence of amino acids in a protein. This will normally alter the shape and function of the protein.
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Are **mutations** *common* or *rare*!?
Mutations are comparatively **rare** events in eukaryotes as our cells can detect incorrect many mistakes in the DNA sequence
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Why are changes in the DNA sequence often **neutral**!?
As mutation doesn’t take place on active site
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When is a mutation **inherited**!?
If the mutation occurs during meiosis in **gamete** formation, it will affect all of the cells in the individual which develops from the gametes. This means the mutation is **inherited**
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When is a mutation **not inherited**!?
If the mutation occurs in a **body cell**, it will affect only those cells produced by mitosis from the effected cell. Mutations in body cells give rise to cancers of the cells that are affected. This type of mutation is **not** inherited.
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What are **mutagens** !?
Mutations are chemicals which cause more frequent mutations
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Examples of **mutagens**:
. **Ionising radiations**(x and gamma ray, ultraviolet light)
. and some chemicals e.g. in tobacco
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Do mutations *increase* or *decrease* **genetic variation** in a population!?
Mutations **increase genetic variation** in a population
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An example of a **mutation**:
Blue eyes (originally brown)
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What *observations* was **Darwin’s theory of evolution** based on !?
. All living things organisms show **variation**
. All living things tend to over-reproduce
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Why will there be a struggle for existence according to Darwin’s ‘**survival of the fittest**’ theory?!
There will be a “struggle for existence” because **organisms over reproduce**, and therefore **resources will be limited**
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Why are there **organisms better adapted to their environment than others** according to Darwin’s ‘**survival of the fittest**’ theory?!
Some organisms will be **better adapted to their environment** than others because they vary
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What happens to the **best adapted** according to Darwin’s **survival of the fittest** theory?
The **best** adapted will **survive** and **reproduce** in greater numbers than the less well adapted
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*Modern interpretation* of Darwin’s **survival of the fittest** theory:
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What are **antibiotics** !?
Antibiotics are chemicals that kill bacteria and do not usually harm animal cells
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How do **antibiotics** kill bacteria only !?
The achieve this by targeting cell structures, such as bacterial cell walls, which animal cells do not contain
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How has *natural selection* lead to the **antibiotic resistance** of **penicillin** !?
